EXCHANGE 


THE  CHEMISTRY  OF  GERMANIUM 


0F  THE 

UNIVERSITY 


A  THESIS 

PRESENTED  TO  THE  FACULTY  OF  THE  GRADUATE  SCHOOL 
OF  CORNELL  UNIVERSITY  FOR  THE  DEGREE  OF 

DOCTOR  OF  PHILOSOPHY 


BY 


FRANK  WILLIAM  DOUGLAS 

4 

September,  1919 


ACKNOWLEDGEMENT 

These  investigations  were  undertaken  at  the  suggestion  and 
under  the  direction  of  Professor  L.  M.  Dennis.  The  author  wishes 
to  express  his  gratitude  for  the  invaluable  aid  received.  He  wishes 
also  to  acknowledge  his  indebtedness  to  Mr.  A.  W.  Bull  who  as- 
sisted in  getting  the  work  started;  to  Mr.  R.  W.  G.  Wyckoff  for 
help  in  making  the  spectrum  analyses  and  in  reading  the  spectro- 
graphs ;  and,  to  the  New  Jersey  Zinc  Company  for  the  supply  of 
"germanium  concentrates"  which  made  the  investigations  possible. 

NOTE:  Much  of  the  experimental  work,  which  led  to  negative 
results  or  which  the  author  regards  as  inconclusive,  has  been 
omitted.  However  the  conclusions  have,  for  the  most  part,  been 
retained.  The  original  thesis  is  deposited  in  the  library  of  Cornell 
University. 


THE  HISTORY  AND  SOURCES 


In  1872  Mendeleef1  from  a  vacancy  in  the  carbon  group  of  his 
periodic  table  predicted  the  existence  of  a  new  element  which  he 
called  ekasilicon.  Its  position  in  the  table  lay  between  silicon  and 
tin.  From  the  properties  of  elements  of  the  same  series,  and  of 
the  same  group,  in  the  periodic  table  Mendeleeff  predicted  many 
of  the  physical  and  chemical  properties  of  the  element  and  its 
principal  compounds.  These  predictions  were  strikingly  verified 
and  the  remarkable  utility  of  the  periodic  table  was  firmly  estab- 
lished by  the  discovery  in  1886-  of  a  new  element,  named  by  its 
discoverer  Germanium,  and  a  little  later  recognized  by  him  to  be 
MendeleefFs  ekasilicon. 

The  element  was  discovered  in  a  new  silver  mineral,  argyrodite, 
a  silver  thio  germanate  (Ag4GeS4.2Ag2S),  first  found  as  an  incrus- 
tation on  other  silver  ores  at  Freiberg,  Germany3,  and  later  found 
in  Bolivia4.  When  pure  it  contained  6.67%  of  germanium  but  as 
it  occurred  as  an  incrustation,  the  germanium  content  of  the  Frei- 
burg ore  was  not  greater  than  0.36%.  This  supply  is  now  practi- 
cally exhausted. 

Germanium  has  also  been  reported  in  euxenite*,  smarskite,  tan- 
talite,  fergresonite,  niobite,  gadolinite",  canfieldite7,  frankeit8,  and 
in  certain  zinc  blendes9,  10,  ". 

A  recently  discovered  source  of  Germanium1-  which  appears  to 
be  the  richest  one  now  available,  is  a  zinc  oxide  residue,  obtained 
as  a  by-product  in  the  purification  of  zinc  from  certain  American 
ores. 

The  material  used  as  a  source  of  germanium  in  the  work  to  be 
described,  was  of  this  character.  It  was  presented  to  this  labora- 
tory by  the  New  Jersey  Zinc  Company. 

'Ann.,  Supp.  Bd.  8,  (1872),  200. 

-Clemens  Winkler,  Ber.,  19,   (1886),  210. 

:'Jahrb.   Miner.,  (1886)  II,  67. 

4Penfield,  Am.   J.   of   Sci.,    (3)   46,    (1893)    107. 

r'Kruss,  Ber.,  21   (1888)   181. 

«K.  v.   Chrustschoff,   Z.   Krystall.,  24,   (1895)    516. 

7Penfield,  Am.  J.  of  Sci.,  (3)  47,  (1894)   451. 

"Stelzner,  Jahrb.  Miner.,   (1893)   II,  119. 

*Urbain,  Compt.  rend.,  149,  (1909)  602. 

10Hillebrand  and  Scherrer,  J.   Ind.    Eng.   Chem.,  8,   (1916)   225 

uBuchanan,  J.  Ind.   Eng.  Chem.,  8,   (1916))   585. 

12Buchanan,  J.  Ind.    Eng.   Chem.,  9,   (1917)   661. 


547911 


EXTRACTION  OF  GERMANIUM 


Winkler1  fused  the  finely  pulverized  argyrodite  ore  in  a  Hes- 
sian crucible  with  a  mixture  of  soda  and  sulphur.  The  powdered 
melt  was  extracted  with  boiling  water.  The  insoluble  residue 
was  repeatedly  subjected  to  the  same  treatment  until  free  from 
germanium. 

Kriiss2  decomposed  euxenite  with  potassium  bisulphate  and 
after  extracting  the  mass  with  hydrochloric  acid,  dissolved  the 
germanium  with  ammonium  sulphide. 

Urbain3  Blondel  and  Obiedoff  decomposed  zinc  blendes  by  heat- 
ing with  concentrated  sulphuric  acid,  and  then  extracted  the  mass 
with  water.  The  insoluble  residue  was  repeatedly  treated  by  this 
method  until  all  the  germanium  was  removed. 

Buchanan4  dissolved  the  zinc  oxide  in  concentrated  hydrochloric 
acid  and  removed  the  germanium  by  distillation  in  a  current  of 
chlorine  gas. 

Winkler5  describes  a  method  of  fusing  the  material  with  potas- 
sium carbonate  and  potassium  nitrate,  dissolving  the  mass  in  water, 
and  after  expelling  the  nitric  acid  by  evaporation  with  sulphuric 
acid,  diluting  and  allowing  the  germanium  dioxide  to  settle  out. 

Gilchrist,  working  in  this  laboratory  on  the  material  above  de- 
scribed, treated  the  concentrate,  in  15  pound  lots,  with  dilute 
sulphuric  acid  (6  N)  and  enough  nitric  acid  to  assure  complete 
oxidation  of  the  germanium.  The  mass  was  evaporated  to  sulphur 
trioxide  fumes  in  a  porcelain  lined  iron  pan.  Commercial  sul- 
phuric acid  was  added  from  time  to  time  until  the  mass  was  no 
longer  lumpy.  Water  was  added ;  the  mixture  was  boiled  and  al- 
lowed to  stand  until  the  precipitate  settled.  The  clear  liquid  was 
decanted  off.  The  precipitate  was  extracted  by  boiling  with  am- 
monium sulphate  (commercial  sulphuric  acid  and  ammonium 
hydroxide)  to  dissolve  out  remaining  germanium.  The  solution 
was  brought  to  an  acidity  of  six  normal,  cooled,  and  saturated 
with  hydrogen  sulphide.  The  precipitate  was  filtered  and  con- 
verted to  oxides  by  means  of  concentrated  nitric  acid  and  ignition. 

!J.   Prakt.  Chem.,  34,  (1886)   192. 
2Ber.,  21,   (1888)   131. 
3Compt.  rend.,  149,   (1909)  602. 
<J.  Ind.  Eng.  Chem.,  8,  (1916)  585. 
6J.  Prakt.  Chem.,  36,  (1887)  185. 


Extraction  with  Dilute  Sulphuric  Acid  and  Precipitation  with 
Hydrogen  Sulphide. 

Solution  of  the  Concentrates. — About  42  Kg.  of  the  concen- 
trates was  treated  in  the  following  maner :  approximately 
six  normal  sulphuric  acid  was  prepared  by  mixing  in  a  No.  12 
evaporating  dish  1  1.  of  commercial  sulphuric  acid  with  5  1.  of 
water.  While  the  solution  was  still  hot,  the  concentrates  were 
added,  in  small  portions,  with  constant  stirring.  After  a  few 
such  additions,  the  temperature  rose  nearly  to  the  boiling 
point  and  effervescense  was  violent.  Addition  of  concentrates 
was  continued  until  further  additions  caused  no  effervescence. 
This  required  about  1.5  Kg. 

The  precipitate  was  allowed  to  settle,  and  as  soon  as  the 
dish  was  cool  enough  to  handle,  the  solution  was  filtered 
using  a  large  Buchner  funnel.  The  rapidity  of  the  extraction 
depended  greatly  on  the  character  of  these  sulphate  precipi- 
tates. Some  were  granular,  settling  rapidly,  and  filtration  was 
finished  in  a  few  minutes.  Others  were  more  flocculent  and 
required  several  hours  to  complete  the  filtration.  The  addition 
of  a  little  water  immediately  after  the  concentrates  were  dis- 
solved aided  in  giving  a  rapid  filtration1.  A  spectroscopic  test 
of  the  precipitate  showed  zinc,  lead,  cadmium,  and  traces  of 
gallium  and  germanium. 

The  Sulphate  Precipitates. — These  precipitates,  consisting 
mainly  of  lead  sulphate,  were  collected  and  heated  in  a  No.  12 
evaporating  dish  with  normal  sulphuric  acid.  The  solution  was 
decanted,  and  the  residue  was  treated  with  six.  normal  sul- 
phuric acid.  The  treatment  was  repeated  using  N/10  sulphuric 
acid.  The  mixture  was  continuously  agitated  by  means  of 
compressed  air.  Finally  the  residue  was  filtered  on  a  Buchner 
funnel,  and  washed  with  sulphuric  acid  (6  N)  until  it  no  longer 
gave  a  spectroscopic  test  for  germanium.  The  process  of  wash- 
ing was  slow  and  tedious,  but  was  much  prolonged  by ;  the 
simultaneous  extraction  of  gallium2.  These  washings  gave 
about  one-half  of  the  yield  of  germanium. 

Precipitation  with  Hydrogen  Sulphide. — The  filtrates  from 
the  sulphuric  acid  extraction  were  placed  in  large  glass  cylin- 
ders, one-fifth  volume  of  commercial  sulphuric  acid  was  added, 

*It  was  found  later  that  if  the  dish  were  heated  just  below  boiling,  the  lead  sulphate 
granulated  and  settled  out,  rendering  nitration  easy.  For  heating  an  asbestos  collar  rest- 
ing on  a  tripod  covered  with  gauze  was  used. 

"A  normal  solution  of  sulphuric  acid  is  recommended  when  germanium  alone  is  to  be 
extracted. 


and  the  solution  was  allowed  to  stand  over  night  to  cool.  Col- 
orless crystals  separated  which,  in  the  spectroscope,  showed 
zinc  only.  To  avoid  this  crystallization  of  zinc  sulphate,  1  1. 
of  water  was  added  to  each  10  1.  of  solution. 

The  solution  was  placed  in  10  1.  bottles  and  hydrogen  sul- 
phide was  passed  through  it  until  most  of  the  precipitate  had 
settled  out  (at  least  an  hour).  After  standing  over  night  to 
complete  the  precipitation,  the  clear  supernatant  liquid  was 
siphoned  off.  The  precipitate  was  filtered  on  a  Buchner  fun- 
nel and  washed  with  a  solution  of  sulphuric  acid  (3  N)  satur- 
ated with  hydrogen  sulphide. 

The  Crude  Sulphides. — When  sucked  dry,  this  precipitate 
was  readily  removed  from  the  paper  by  means  of  a  porcelain 
spatula.  The  filter  papers  with  the  small  amount  of  adhering 
precipitate  were  preserved  for  treatment  to  be  described  later. 
The  precipitate  was  neutralized  with  ammonium  hydroxide, 
evaporated  to  dryness,  and  ground  to  a  fine  powder.  A  spec- 
troscopic  test  showed  large  amounts  of  zinc,  cadmium,  ger- 
manium and  lead.  Much  arsenic  was  also  present. 

The  washings  from  the  sulphate  residue  were  treated  in  a 
similar  manner  and  yielded  about  an  equal  quantity  of  crude 
sulphides. 

Conversion  to  Crude  Oxides. —  The  dried  sulphides  were 
placed  in  a  large  evaporating  dish  and  a  small  portion  of  nitric 
acid  was  added.  The. action  was  very  vigorous  and  care  was 
necessary  to  prevent  loss  by  frothing.  Further  additions  of 
nitric  acid  were  made  until  violent  action  no  longer  occurred 
and  the  mass  was  covered  with  the  acid.  The  dish  was  then 
gently  heated  and  finally  the  solution  was  evaporated  to  dry- 
ness.  Evaporation  with  nitric  acid  was  repeated  until  oxida- 
tion appeared  complete.  The  nitric  acid  was  then  driven  off 
by  heating  until  sulphur  trioxide  fumes  appeared.  If  the  mass 
were  allowed  to  cool  and  solidify,  a  very  hard  enamel  would  be 
formed  which  could  not  be  removed  from  the  dish.  This  was 
avoided  by  stirring  during  the  cooling  which  granulated  the 
mass  and  rendered  grinding  easy.  Some  was  also  neutralized 
with  ammonium  hydroxide,  evaporated  to  dryness  and  ignited 
to  expel  ammonium  sulphate.  This  gave  a  powdery  residue. 
About  870  g.  of  crude  oxides  was  obtained.  A  spectroscopic 
test  of  the  oxides  from  the  washing  of  the  sulphate  residue 
showed  large  amounts  of  zinc,  cadmium,  and  germanium  and 

8 


a  trace  of  gallium.    Much  arsenic  was  also  present.    These  ox- 
ides were  preserved  for  purification  as  described  later. 

The  Filtrate  from  the  Sulphide  Precipitation. — After  filtra- 
tion of  the  sulphides,  the  filtrate  soon  became  cloudy  due  to 
precipitated  sulphur.  These  filtrates  were  stored  in  large  glass 
cylinders.  On  standing  several  weeks  the  solution  became 
clear  while  a  white  flocculent  precipitate  settled  out.  A  spec- 
troscopic  test  of  this  precipitate  showed  zinc,  cadmium,  and 
germanium,  in  moderate  amounts.  A  portion  of  the  solution, 
neutralized  with  ammonium  hydroxide,  evaporated  and  ignited 
to  expel  the  ammonium  sulphate,  showed  in  the  spectroscope 
zinc  only.  The  solution  was  nearly  saturated  with  zinc  sul- 
phate and  other  elements  known  to  be  present  did  not  give  a 
spectrum. 

The  Sulphide  Filters. — These  filters  were  collected  in  a  bottle 
containing  sodium  hydrosulphide  solution.  After  thus  digest- 
ing several  days,  the  solution  was  filtered  on  a  Buchner  funnel 
and  the  residue  washed  with  sodium  hydrosulphide  solution1. 
The  filter  residue  was  burned  in  an  iron  dish  and  the  ash  added 
to  the  filtrate.  After  being  digested  for  several  days,  with  fre- 
quent stirring,  the  solution  was  again  filtered.  A  spectroscopic 
test  of  the  residue  showed  zinc,  cadmium  and  lead,  but  m> 
germanium. 

The  filtrate  was  subjected  to  Winkler's  fractional  precipita- 
tion method2.  Three  liters  of  solution  were  acidified  with  sul- 
phuric acid  so  that  it  contained  less  than  10  cc,  of  six  normal 
acid.  The  precipitate  was  immediately  filtered  and  washed.. 
Three  such  fractional  precipitations,  the  second  and  third  made 
with  solutions  even  nearer  the  neutral  point,  gave  arsenious 
sulphide  precipitates  containing  considerable  amounts  of  ger- 
manium sulphides,  and  filtrates  in  which  germanium  sulphide 
formed  even  while  filtering.  The  latter  was  always  distinctly 
tinged  with  yellow.  The  method  gave  only  partial  separations 
of  arsenic  and  germanium.  All  precipitations  were  made  in 
cold  solutions. 


'Prepared    by    saturating    NaOH    solution    (3    N)    with    hydrogen    sulphide    until    it    gave  a 
strong  odor  of  the  gas. 

-J.    Prakt.    Chem.   142,    (1886)    193. 


PURIFICATION  OF  THE  GERMANIUM 


The  chemical  behavior  of  arsenic  and  germanium  are  so  similar 
that  their  separation  is  the  most  difficult  problem  in  the  purifica- 
tion of  germanium.  However,  unexpected  difficulty  was  encoun- 
tered in  the  persistence  of  zinc  in  being  carried  down  with  ger- 
manium disulphide  when  a  strongly  acid  solution  containing  these 
elements  was  saturated  wth  hydrogen  sulphide. 

Winkler1  purified  germanium  by  a  process  of  fractional  precipita- 
tion. He  made  the  sodium  sulphide  solution  from  argyrodite,  al- 
ready mentioned,  just  acid  with  sulphuric  acid,  thus  precipitating 
arsenic  and  antimony  as  sulphide,  and  then  recovered  the  ger- 
manium by  precipitating  it  from  the  nitrate  with  hydrogen  sulphide, 
after  making  the  filtrate  strongly  acid  with  hydrochloric  acid. 
Later2  he  recognized  this  product  as  impure  and  modified  the 
process  by  precipitating  with  sulphuric  acid,  first  from  the  slightly 
alkaline  solution  (antimony  and  most  of  the  arsenic),  then  from  a 
slightly  acid  solution  (arsenic  and  germanium),  and  finally  from 
the  strongly  acidified  solution  (most  of  the  germanium).  This 
product  was  still  impure,  and  after  oxidizing  with  nitric  acid  and 
igniting,  the  residue  was  further  purified  by  dissolving  in  hydro- 
fluoric acid  and  precipitating  with  potassium  fluoride.  The  potas- 
sium fluogermanate  was  recrystallized.  This  certainly  should  have 
given  a  pure  product. 

Urbain,  Blondel,  and  ObiedofT,  working  on  zinc  blendes,  used  a 
somewhat  similar  method  of  purification  but  introduced  some  new 
features.  They  extracted  zinc  from  the  sulphides  by  digesting  with 
15%  sulphuric  acid. 

After  repeated  treatments  with  sodium  sulphide  and  sulphuric 
acid,  the  sulphides  were  finally  precipitated  from  a  hydrochloric 
acid  solution,  redissolved  in  ammonium  hydroxide,  and  the  arsenic 
and  traces  of  molybdenum  separated  from  germanium  by  cautious 
fractional  precipitation  with  hydrochloric  acid.  They  say  that 
perfectly  white  germanium  sulphide  was  obtained  from  the 
solution. 

The  author  found  that  precipitation  in  hydrochloric  acid  solution 

'J.  prakt.  Chem.,  34  (1886)  193. 
»J.    Prakt.    Chem.,  3«,    (1887)    183. 

10 


gave  a  purer  product  than  that  from  sulphuric  acid,  also,  that  solu- 
tion in  ammonia  gave  a  better  separation  than  that  in  sodium 
sulphide.  Nevertheless,  he  doubts  the  purity  of  the  perfectly  white 
sulphide. 

Buchanan1  obtained  a  nearly  pure  germanium  solution  by  distilling 
the  zinc  oxide  concentrates  with  hydrochloric  acid  in  a  current  of 
chlorine.  In  small  amounts  he  purified  the  product  by  precipitating 
with  hydrogen  sulphide,  oxidizing  the  germanium  disulphide  with 
nitric  acid,  and  preparing  potassium  fluogermanate  from  the  resi- 
due. This  should  have  given  a  pure  compound  of  germanium. 

Bardet-  prepared  germanium  dioxide  from  the  residue  left  after 
evaporation  of  certain  mineral  waters.  His  method  was  similar  to 
Winkler's  but  he  used  magnesia  mixture  to  precipitate  the  arsenic. 
He  traced  the  action  of  germanium  by  means  of  the  spectroscope. 

The  author  found  that  magnesia  mixture  precipitates  germanium 
almost  completely  so  that  it  is  likely  much  germanium  was  lost  by 
this  method  of  separation.  The  volatility  of  arsenic  and  magne- 
sium in  the  precipitate  would,  undoubtedly,  account  for  the  failure 
of  the  spectroscope  to  detect  germanium  if  present. 

EXPERIMENTAL 

Ignition  of  the  Crude  Sulphides. — As  both  the  oxides  and  sul- 
phides  of  arsenic  are  very  volatile  while  germanic  sulphide  is  only 
slightly  so,  and  is  easily  converted  by  ignition  in  air  to  the  non- 
volatile germanic  oxide,  effort  was  made  to  separate  these  elements 
by  ignition  of  their  sulphides  in  a  current  of  air,  and  later  in  a 
current  of  oxygen.  The  sample  of  crude  sulphides  used  was  the 
dried  precipitate  described  under  "Extraction  of  the  Germanium." 
(p.  8.) 

Ignition  of  Crude  Sulphides  in  a  Current  of  Air. — The  sulphides, 
contained  in  a  porcelain  boat,  were  ignited  in  a  hard  glass  tube, 
the  heat  beng  raised  gradually  to  dull  redness.  A  current  of  com- 
pressed air  was  passed  through  the  tube  and  slowly  bubbled 
through  dilute  sodium  hydroxide  solution. 

The  characteristic  coatings  for  ignition  of  arsenious  sulphide 
were  obtained  just  beyond  the  boat.  This  sublimate  rinsed  into  a 
dish  and  evaporated  to  dryness  gave  no  test  for  germanium  in  the 
spectroscope. 

Fumes  were  given  off  which  were  only  partially  absorbed  by  the 


3J.  Ind.   Eng.  Chem.,  8,   (1916)   585. 
-Compt.  rend.,  158,  (1914),  1279. 


11 


sodium  hydroxide  solution.  They  appeared  to  consist  of  volatilized 
sulphur.  The  sodium  hydroxide  solution  was  made  six  normal 
with  sulphuric  acid  and  saturated  with  hydrogen  sulphide.  A  pale 
yellow  precipitate  was  obtained  which  showed  no  germanium  in 
the  spectroscope  test. 

The  residue  in  the  boat  subjected  to  Marsh's  test,  using  the  silver 
nitrate  modification,  gave  arsenic  still  present  in  abundance. 

Ignition  of  Pure  Oxides  of  Arsenic  and  Germanium. — In  order 
to  verify  the  above  conclusion,  and  eliminate  the  effect  of  traces 
of  other  elements  still  remaining  after  the  above  purification,  pure 
germanium  dioxide  and  arsenious  oxide  were  evaporated  with 
nitric  acid  until  the  arsenic  was  converted  to  the  pentavalent 
form,  and  then  ignited  in  a  porcelain  dish  to  a  red  heat.  A  Marsh's 
test  of  the  residue,  using  the  silver  nitrate  modification,  showed  a 
large  amount  of  arsenic  still  present,  thus  proving  that  arsenic 
is  not  separated  by  ignition  with  germanium  even  when  other 
elements  are  completely  excluded. 

Conclusions  from  Experiments  on  Ignition. — Germanium  is  not 
appreciably  volatilized  by  ignition  in  air  even  when  in  the  form  of 
germanium  disulphide. 

Arsenic  is  not  expelled  by  ignition  to  redness  when  mixed  with 
germanium,  in  the  form  of  concentrates,  of  sulphides,  oxides,  or 
even  of  the  pure  oxides  of  the  two  elements  with  other  bases  ab- 
sent. Ignition  with  an  acid  less  volatile  than  the  oxides  of  arsenic 
does  not  cause  complete  volatilization. 

The  fact  that  pure  oxides  of  arsenic  and  germanium  are  not 
separated  by  ignition  suggests  the  possibility  of  an  arsenate  or 
pyroarsenate  of  germanium,  as  the  formation  of  a  phosphate  of 
germanium  has  already  been  noted1. 

The  partial  separation  of  arsenic  by  volatilization  of  the  oxides, 
as  described  above,  appears  to  be  a  convenient  method  of  prevent- 
ing the  accumulation  of  arsenic  in  by-products,  thus  making  pos- 
sible a  practically  complete  separation  of  arsenic  from  germanium 
by  the  method  of  precipitation  as  potassium  fluogermanate  to  be 
described  later. 

Formation  of  Potassium  Fluogermanate  from  Crude 
Oxides. — The  double  salt  potassium  fluogermanate  is  easily 
formed,  very  crystalline,  and  much  more  soluble  in  hot  than 
in  cold  water.  It  is,  therefore,  very  suitable  for  purification  by 


'Winkler,  J.   Prakt.   Chem.,  34,   (1886)   211. 

12 


crystallization  as  arsenic  does  not  form  such  a  double  salt. 
These  experiments  were  designed  to  effect  a  separation  from 
accompanying  elements  by  this  method. 

Commercial  hydrofluoric  acid  was  used  in  these  prepa- 
rations.   Two  determinations  of  the  total  acid  present,  by 
the  method  previously  described,  gave,  respectively,  43.43% 
and  43.41%  calculated  as  hydrofluoric  acid. 
Crystallized  potassium  fluoride  was  also  used. 

First  Method. — In  a  large  lead  dish,  98.5  g.  of  crude 
oxides  was  treated  with  149  g.  of  hydrofluoric  acid 
(20%).  The  mixture  was  heated  on  a  water  bath  to 
dissolve  as  much  as  possible  of  the  white  precipitate 
formed.  The  solution  was  filtered,  and  washed  with 
hot  water  which  dissolved  any  remaining  white  pre- 
cipitate but  left  a  gray  insoluble  residue. 

Forty  grams  of  potassium  fluoride  was  added  to  the 
filtrate  and  the  solution  was  evaporated  to  a  volume 
of  about  150  cc.  The  solution  was  allowed  to-  stand 
over  night  when  a  mass  of  fine  white  crystals  formed. 
These  were  filtered,  washed  with  cold  water,  dilute 
alcohol  (1 :1),  and  95%  alcohol,  then  dried  in  the  oven. 
The  yield  was  67.0  g.  A  spectroscopic  test  showed 
zinc,  potassium,  germanium,  and  a  little  gallium. 

The  filtrate  was  evaporated  to  one-third  volume 
and  set  aside  to  crystallize.  A  mass  of  fine  white 
-crystals  formed  which  were  recrystallized  as  de- 
scribed later. 

Second  Method.^-In  a  large  lead  dish  466  g.  of  crude 
oxides  were  treated  with  346  g.  of  commercial  hydro- 
fluoric acid  and  494  cc.  of  water  (approximately  20% 
hydrofluoric  acid).  The  mixture  was  stirred  with  a 
platinum  spatula  to  effect  solution  as  far  as  possible. 
Without  filtering,  a  solution  consisting  of  330  g.  pot- 
assium fluoride,  dissolved  in  1014  cc.  of  water,  was 
added.  This  solution  was  evaporated  to  about  800  cc. 
and  allowed  to  stand  over  night.  A  gray  crystalline 
precipitate  formed,  which  was  filtered,  washed  with 
.cold  water,  dilute  alcohol  (1 :1),  and  95%  alcohol,  and 
•dried  in  the  oven.  The  yield  was  196.5  g.  A  spectro- 
scopic test  gave  zinc,  germanium,  and  potassium. 

13 


The  filtrate  was  evaporated  to  a  volume  of  500  cc. 
and  set  aside  to  crystallize.  It  yielded  a  white  crystal- 
line product  weighing  140  g.  A  spectroscopic  test 
showed  potassium,  zinc,  and  cadmium,  but  no  ger- 
manium. 

The  second  filtrate  was  evaporated  to  350  cc.  It 
gave  a  similar  product  weighing  133.5  g.  and  showing 
in  the  spectroscope  zinc  and  cadmium  but  no  line  of 
germanium. 

The  crude  oxides  treated  by  these  two  methods 
weighed  867  g.  About  145  g.  of  the  first  product  of 
crystallization  was  prepared  by  the  first  method 
and  250  g.  by  the  second.  Arsenic  was  not  found  by 
the  spectroscopic-  tests,  but  was  undoubtedly  present 
in  these  products. 

Recrystallization  of  the  -Potassium  Fluogermanate. — 
The  first  product  of  crystallization  by  the  second  method 
was  transferred  to  a  three  liter  lead  dish  and  extracted 
repeatedly  by  boiling  with  water.  The  solution  from  each 
extraction  was  decanted  through  a  filter  held  in  a  rubber 
funnel.  About  10  1.  of  solution  was  thus  obtained.  A  gray 
residue  was  left  on.  the  filters  which  Was  preserved  for 
further  treatment. 

The  water  extract  ,was  evaporated  to  about  6  1.  in  an 
8  1.  lead  dish  and  allowed  to  crystallize  over  night.  The 
crystals  were  filtered  out,  washed  with  cold  water,  and 
dried  in  the  oven. 

To  the  mother  liquor,  was  added  the  first  product  of 
crystallization  from  the  first  method  and  the  volume  was 
made  up  to  8  1.  The  dish  was  heated  over  an  asbestos 
collar  supported  on  a  wire  gauze.  Boiling  was  continued 
until  solution  was  practically  complete.  The  solution 
was  evaporated  to  6  1.  and  allowed  to  crystallize.  The 
crystals  were  filtered,  washed,  and  dried  as  before.  The 
yield  of  the  recrystallization  was  151  g. 

The  product  was  again  recrystallized.  Fifteen  grams 
was  boiled  with  about  400  cc.  of  water  in  a  platinum  dish 
until  the  solution  was  saturated.  The  residue  settled 
quickly  and  the  supernatant  liquid  was  decanted  through 
a  filter  held  in  a  rubber  funnel.  Extraction  was  repeated 
until  the  volume  of  the  filtrate  was  about  600  cc.  The 

14 


filtrate  was  received  in  a  700  cc.  platinum  dish.  It  was 
boiled  down  to  a  volume  of  400  cc.,  using  the  free  flame  of 
a  Bunsen  burner.  The  solution  was  quickly  cooled  by 
placing  the  dish  in  cold  water.  This  caused  it  to  form  a 
jelly-like  mass.  A  little  stirring  would  cause  the  jelly  to 
disappear  leaving  a  fine  granular  precipitate.  Stirring, 
however,  was  not  necessary. 

After  standing  about  three  hours  or  over  night,  as  was 
most  convenient,  the  white  finely  crystalline  mass  was 
filtered,  using  paper  held  in  a  rubber  funnel,  and  was 
washed  twice  with  cold  water.  The  process  of  crystalliza- 
tion was  repeated  by  adding  to  the  mother  liquor  enough 
of  the  product  of  the  first  recrystallization  to  saturate  a 
volume  of  solution  equal  to  the  capacity  of  the  dish,  then 
boiling  to  effect  solution,  filtering,  and  extracting  repeat- 
edly with  hot  water  until  the  dish  was  filled.  The  solution 
was  then  evaporated  to  saturation  and  treated  as  above 
described.  When  about  50  g.  of  crystals  had  been  obtained, 
the  mass  was  washed  with  cold  water,  dilute  alcohol  (1:1), 
and  95%  alcohol,  successively.  All  the  product  of  the  first 
crystallization  was  worked  over  in  this  way. 

A  dark  gray  residue  was  left  on  the  filters.  This  was 
combined  with  the  residue  from  the  first  crystallization. 
To  this  was  added  a  solution,  obtained  by  digesting  with 
boiling  water  all  the  filters  used  in  filtering  the  potassium 
fluogermanate.  Extraction  of  the  residue  was  then  carried 
out  as  described  above.  It  was  continued  to  the  first  ap- 
pearance of  a  white  amorphous  residue  unlike  the  potas- 
sium fluogermanate.  This  was  taken  as  indicating  danger 
of  contamination. 

The  portions  of  potassium  fluogermanate  thus  obtained 
were  dried  in  an  electric  oven  for  several  days  at  108°  G, 
thoroughly  mixed  and  preserved  as  sample  No.  2.  The 
yield  was  126  g.  Proofs  of  the  purity  will  be  given  under 
the  analysis  of  potassium  fluogermanate. 

The  gray  residue  still  left  on  the  filter  was  further  ex- 
tracted by  boiling  with  water  until  very  little  solid  sepa- 
rated on  evaporating  and  cooling  the  extract.  The  residue 
was  tested  in  the  spectroscope  and  showed  zinc,  iron, 
calcium,  and  lead,  but  no  germanium.  Its  weight  was  30  g. 

The  hot  water  extract  was  evaporated  to  crystallization. 

15 


The  crystals,  filtered  and  washed  with  cold  water,  were 
combined  with  those  obtained  by  evaporating  to  the  point 
of  saturation  the  mother  liquor  from  the  first  recrystal- 
lization  of  the  potassium  fluogermanate. 

This  white  crystalline  mass  was  recrystallized  by  ex- 
traction with  boiling  water  in  the  manner  above  described. 
Extraction  was  continued  until  jellying  no  longer  took 
place  on  evaporating  the  solution  and  cooling.  The  crys- 
tals obtained  were  washed,  dried  and  preserved  as  sample 
No.  3.  The  yield  was  36  g. 

A  residue  was  left  on  the  filter  which  showed  in  the 
-spectroscope  calcium  fluoride,  and  potassium,  but  no 
--•germanium. 


16 


ANALYSIS  OF  POTASSIUM  FLUOGERMANATE 


The  purpose  of  this  analysis  was  to  establish  its  purity  and 
thereby  prove  the  accuracy  of  the  method  of  purification.  Serious 
difficulties  were  encountered  at  every  hand  because  of  the  peculiar 
properties  of  germanium  and  its  interference  with  established 
methods. 

The  samples  have  already  been  described.  No.  1  was  obtained 
from  the  germanium  dioxide,  prepared  from  the  sulphide  filters, 
and  partially  purified  by  Winkler's  method  of  fractional  purifica- 
tion. No.  2  was  the  main  body  of  the  double  salt,  prepared  from 
the  crude  oxides,  by  the  method  described  under  "Purification  of 
Germanium",  (p.  15.) 

Spectroscopic  Tests  and  Solubility. — No.  1  gave  on  testing  with 
the  spectroscope  only  potassium  and  germanium.  No.  2  gave 
by  the  same  test  potassium,  germanium,  and  a  possibility  of  a 
trace  of  calcium.  As  the  carbons  used  in  forming  the  arc  con- 
tained small  amounts  of  iron,  sodium  and  calcium,  the  test  was 
not  conclusive  for  these  elements.  The  calcium  lines  appeared  to 
be  enhanced  by  the  presence  of  fluorine  rendering  the  test  for  that 
element  still  more  uncertain. 

Both  samples  were  soluble  in  40  parts  of  boiling  water  having 
no  detectable  trace  of  solid.  The  solution  appeared  perfectly  clear 
thus  excluding  more  than  a  trace  of  calcium  fluoride. 

Test  for  Arsenic. — Twenty-five  hundredths  of  a  gram  of  Sample 
No.  2  was  dissolved  in  30  cc.  of  boiling  water.  Sodium  carbonate 
solution  was  added  until  the  solution  was  alkaline  to  litmus  paper. 
Seven  and  one-half  cc.  of  calcium  chloride  solution  (1:10)  was 
added.  This  caused  the  litmus  paper  to  turn  red.  The  precipitation 
of  calcium  fluoride  causes  a  strong  acid  reaction,  perhaps,  accord- 
ing to  the  equation  : 

K2GeF(i-f3CaCl,-f4H2O=3CaF2-f2KCl+4HCl-hH4GeO4 
Sodium  carbonate  was  added  to  a  faint  alkaline  reaction.    The  so- 
lution was  boiled,  and  allowed  to  stand  on  the  hot  plate  until  the 
precipitate  settled.     The  precipitate  was  filtered  and  washed  with 
hot  water. 

The  precipitate  was  rinsed  into  a  platinum  dish  and  evaporated 
to  dryness.  The  residue  was  moistened  with  water,  6  cc.  of  sul- 

17 


phuric  acid  was  added,  and  the  mass  was  evaporated  to  expel  the 
hydrofluoric  acid.  Water  was  added  and  the  solution  was  sub- 
jected to  Marsh's  test  using  the  silver  nitrate  modification.  Very 
little  precipitation  of  silver  occurred.  The  final  test  gave  a  slight 
precipitate  resembling  sulphur.  It  was  filtered,  washed,  oxidized 
with  potassium  chlorate  and  hydrochloric  acid,  and  subjected  to 
Marsh's  spot  test.  No  trace  of  arsenic  could  be  detected. 

The  filtrate  was  subjected  to  Marsh's  test  using  the  silver 
nitrate  modification.  A  very  slight  precipitate,  resembling  sulphur, 
was  obtained  which  was  oxidized  with  potassium  chlorate  and 
hydrochloric  acid,  and  subjected  to  Marsh's  spot  test.  No  trace 
of  arsenic  was  found. 

In  each  case  the  gas  was  passed  through  the  silver  nitrate  solu- 
tion for  about  one  hour. 

These  tests  assured  a  high  grade  of  purity  for  the  potassium 
fluogermanate,  as  the  accompanying  elements  which  \vere  present 
in  appreciable  quantities  in  the  original  material  were  thus  shown 
to  be  eliminated,  and  the  process  of  preparation  did  not  tend  to 
accumulate  traces  of  others. 

Loss  on  ignition. — Kriiss  and  Nilson1  heated  potassium  fluo- 
germanate in  a  covered  crucible  to  beginning  red  heat.  It  lost 
0.43%  of  "water  of  decrepitation."  They  state  that  it  was  then 
heated  to  a  strong  red  heat  for  some  time  when  it  did  not  melt, 
but  remained  unchanged  and  showed  no  decrease  in  weight. 

On  the  other  hand,  Winkler2  gives  a  series  of  determinations 
showing  losses  ranging  from  0.41%  by  heating  one  minute  in  a 
covered  crucible  at  dark  red  heat  to  29.017%  on  heating  one  hour 
at  full  red  heat  in  an  open  crucible. 

Direct  Ignition. — Exactly  one  gram  of  sample  No.  2  was 
weighed  in  a  platinum  crucible,  covered,  and  ignited  carefully 
at  a  dull  red  heat,  the  bottom  of  the  crucible  just  showing 
the  color.  The  crucible  was  cooled  and  weighed.  The  igni- 
tion was  repeated  but  a  constant  weight  was  not  obtained.  A 
slight  decrepitation  was  evidenced  by  the  appearance  of  the  • 
salt.  No  signs  of  fusion  were  noted  beyond  a  little  cohe- 
sion of  the  salt.  No  evidence  of  volatilization  or  sublimation 
could  be  detected.  The  data  are  as  follows : 

lBer.,  2»,   (1887)   1698. 

2J.  prakt.  Chem.,  M,  (1887)  202. 


18 


Weight  of  Crucible  and  K,GeF0 21.4256  g. 

Ditto,  ignited  10  min.  at  dull  red  heat 21.4137  g. 

Ditto,  ignited  again  10  min.  at  dull  red  heat  .  .  .  .21.4011  g. 

Ditto,  ignited  again  20  min.  at  dull  red  heat  .  . .  .21.3833  g. 


Loss  in  weight 0.0423  g. 

Percentage  of  loss — 4.23. 

/- 

Ignition  in  a  Snowdon  Furnace1. 

The  furnace  used  was  modified  by  using  for  the  heating 
chamber  a  small  porous  cup  wound  with  nichrome  wire.  The 
salt  was,  weighed  in  a  platinum  crucible  of  such  size  that  it 
rested  in  the  porous  cup  with  only  a  few  millimeters  of  the 
rim  protruding.  The  crucible  was  heated  first  in  the  electric 
oven,  then  in  the  air  oven,  and  finally  in  the  Snowdon  Furnace. 
Regulation  of  the  temperature  was  obtained  by  means  of  a 
bank  of  lamps  connected  to  a  110  volt  direct  current  circuit. 
The  furnace  was  placed  in  series  with  the  bank  of  lamps  and 
was  calibrated  by  means  of  a  high  temperature  mercury  ther- 
mometer. The  temperature  was  increased  by  the  addition  of 
a  lamp  at  a  time  to  the  circuit  until  the  safe  working  capacity 
of  the  furnace  had  been  reached.  The  data  are  as  follows : 
Loss  on  Ignition  in  a  Snowdon  Furnace. 

Weight  of  Sample  2  of  K,GeFr,  v.  ...;..>.....  -..  1.0000  g. 

Weight  of  Platinum  Crucible  and  Sample 21.4682  g. 

Ditto,  dried  2  hrs.  in  an  electric  oven  at  112°C.  .21.4682  g. 

Loss 0.0000  g. 

Dried  in  an  air  oven  at  125-126°C 21.4682  g. 

Loss    ' .0000  g. 

Dried  in  an  air  oven  at  156-160°C 21.4680  g. 

Loss 0002  g. 

Heated  in  Snowdon  Furnace  (for  2.  hrs.) 

at   190°C .21.4680  g. 

Loss    . 0000  g. 

Ditto,  at  262°C.  (1  hr.) .21.4680  g. 

Loss 0000  g. 

Ditto,  at  338°C.  (1  hr.) '".. 21.4679  g. 

Loss .0001  g. 

Total  loss    0003  gm. 

Ditto,  at  44D°C,  (50  minutes) 21.4679  g. 

Loss 0000  g. 


'The  Cornell  Chemist,   May,  1914. 

19 


Determination  of  Water. 

This  was  the  first  of  the  quantitative  determinations   made  in 

order  that  the  formula  proportions  might  be  used  as  a  check  upon 

other  analyses  and  as  a  test  of  purity. 

By  Drying  in  an  Electric  Oven. — Five-tenths  gram  of  Sam- 
ple No.  1  was  weighed  in  a  small  platinum  dish  and  dried  in 
the  electric  oven  at  110°C.  There  \vas  no  loss  in  weight. 

Five-tenths  of  a  gram  of  Sample  No.  2  was  weighed  in  a 
platinum  dish  and  dried  in  the  same  oven  at  105°C.  for  one 
hour.  The  loss  was  0.2  mg.  The  sample  was  dried  for  another 
day  at  105°C 

Test  in  a  Closed  Tube. — Determinations  of  loss  on  ignition 
and  flourine  having  caused  some  doubt  whether  the  composi- 
tion of  the  potassium  fluorgermanate  was  shown  by  the  for- 
mula, a  portion  of  the  salt  was  ignited  in  a  closed  glass  tube 
\vhich  had  been  tested  to  prove  it  free  from  water.  Decrepita- 
tion began  at  once,  at  a  dull  red  heat  the  mass  fused,  the  glass 
was  strongly  etched,  and  water  collected  in  the  cooler  part  of 
the  tube.  As  this  "water  of  decrepitation,"  as  Kruss  and 
Nilson  call  it,  could  not  be  determined  by  the  usual  methods, 
absorption  methods  were  used. 

By  Ignition  in  an  Electric  Furnace  and  Absorption  of  the 
Liberated  Fluoride  by  Passing  Through  Lead  Oxide. 

Apparatus : 

Test  tube  for  regulation  of  air  pressure 

Muencke  gas  wash  bottle  filled  with  H2SO4 

Schwartz  tube  filled  with  glacial  phosphoric  acid 

Electric  .furnace  with  rheostat  and  hard  glass  tube 

Two  Schmitz  tubes 

U-tube  filled  with  CaCl,  (safety) 

Filter  flask 

Chapman  air  pump. 

Test  Tube.  This  was  arranged  to  adjust  the  height  of 
the  water  column.  Excess  of  air  pressure  was  used  causing 
bubbling  through  the  water.  The  height  of  the  water 
column  was  set  so  that  the  sulphuric  acid  in  the  gas  wash 
bottle  was  displaced  almost  to  the  opening.  This  assured 
constancy  of  pressure  and  a  slight  vacuum  in  the  apparatus. 

Combustion  Tube.  This  was  of  hard  glass  and  24  in. 
long.  Diameter  y$  in.  Rubber  stoppers  were  used.  The 

20 


column  of  litharge  was  6  cm.  long.     A  platinum  boat  was 
used. 

Filter  Flask.  This  was  used  to  equalize  any  sudden 
change  in  the  suction.  Excess  of  suction  was  maintained 
with  the  air  pump  and  the  rate  of  bubbling  was  regulated 
by  means  of  a  screw  clamp. 

Rheostat.  This  consisted  of  a  wooden  frame  on  which 
were  mounted  strips  of  tin  plate.  By  connecting  this  across 
the  terminals  of  the  direct  current  supply  and  attaching 
the  apparatus  as  a  shunt,  a  perfect  control  of  the  current 
tip  to  5  amperes  was  obtained. 

Electric  Furnace.  This  was  a  9  in.  section  from  a  mul- 
tiple unit  electric  furnace.  It  was  calibrated  by  means  of 
a  thermocouple. 

Preparation  of  Apparatus  and  Materials. 
Schmitz  Tubes.  Two  were  used  in  series,  both  being 
weighed  separately  for  each  determination.  They  were 
first  thoroughly  washed  with  water  and  dried  by  rinsing 
with  alcohol  and  passing  air  through  them.  They  were 
finally  dried  in  the  electric  oven.  The  glacial  phosphoric 
acid  was  broken  into  coarse  pieces  and  was  held  in  place 
by  perforated  porcelain  plates. 

Hard  Glass  Tube.  It  was  thoroughly  washed,  dried  in  a 
current  of  air,  and  finally  dried  by  heating  in  the  electric 
furnace  for  3  hrs,  with  a  current  of  dry  air  passing 
through  it. 

Litharge.  As  the  supply  on  hand  was  not  satisfactory, 
some  was  prepared  by  heating  red  lead  (Pb3O4)  in  a  hard 
glass  tube  in  the  furnace  for  an  hour  at  700°  C.  The  product 
was  yellow  when  cold.  It  was  tested1  and  found  to  contain 
a  little  chloride.  This  was  washed  out  with  boiling  water. 
The  litharge  was  dried  by  carefully  heating  in  an  iron  pan 
over  a  triple  burner. 

Asbestos  Plugs.  These  were  ignited  in  a  platinum  cru- 
cible over  a  blast  lamp.  They  turned  brown. 

Testing  of  Apparatus.  After  assembling,  the  apparatus 
was  tested  for  leaks  by  causing  it  to  support  a  column  of 
water  15  cm.  high  for  10  min. 

The  apparatus  was  finally  dried  by  running  it  as  a  blank 
determination.  The  empty  end  of  the  tube  was  heated 


JKrausch's   Chemical  Reagents,   3rd   Ed.   p.   159. 

21 


30  min.  at  red  heat,  then  the  furnace  was  moved  to  the 
litharge  end  which  was  heated  for  one  hour  at  500°C. 

A  blank  determination  was  then  run  and  the  weight  of 
the  Schmitz  tubes  remained  constant.  In  spite  of  these 
precautions,  three  determinations  were  run  before  the 
apparatus  became  constant. 

Method.  The  boat  was  ignited,  cooled  in  a  desiccator, 
and  weighed.  One  gram  of  Sample  No.  2  of  potassium 
flougermanate  was  weighed  in  the  boat.  The  boat  was 
placed  in  the  combustion  tube  and  a  current  of  4.5  amp. 
was  passed  through  the  furnace,  thus  heating  the  tube 
rapidly  to  the  desired  temperature.  The  current  was  then 
adjusted  to  maintain  this  temperature. 

Compressed  air  was  bubbled  through  the  test  tube  and 
the  height  of  the  delivery  tube  was  adjusted  to  give  prac- 
tically no  column  of  sulphuric  acid  in  the  purifier  to  dis- 
place. The  suction  was  started  and  the  stop  cocks  in  the 
Schmitz  tubes  were  gradually  opened  until  a  gentle  suc- 
tion was  obtained  through  the  apparatus  and  a  slow  cur- 
rent of  air  was  passing.  Great  care  was  necessary  in 
opening  the  apparatus  as  either  a  back  pressure  or  too 
rapid  flow  of  gas  would  make  refilling  of  the  Schmitz  tubes 
necessary.  A  little  attention  to  the  order  of  opening  the 
stop  cocks  eliminated  this  danger. 

The  end  of  the  tube  containing  the  boat  was  heated  for 
the  chosen  time,  then  the  furnace  was  allowed  to  cool  to 
the  temperature  chosen  for  heating  the  litharge  end,  and 
the  furnace  was  gradually  moved  along  to  this  end  thus 
driving  out  any  adhering  moisture.  After  this  heating, 
the  furnace  was  cooled  rapidly  to  about  100°C.  when  the 
stop  cocks  were  closed  in  the  Schmitz  tubes  and  the  ap- 
paratus disconnected. 

The  Schmitz  tubes  were  handled  with  a  dry  cloth  and 
were  not  wiped.  They  were  allowed  to  stand  near  the 
balance  case  one-half  hour  and  were  opened  for  a  mo- 
ment before  weighing  to  adjust  the  air  pressure.  All  the 
apparatus  was  kept  tightly  stoppered  while  not  in  use. 


Data: 

(a)  Weight  of  Sample  No.  2  of  K2GeF0.  . .  .1.0000  g. 
Absorption  of  1st  Schmitz 

Tube  . . . .....  Wi . ;*.r,j.  ,.,. .     .0066  g. : 

Absorption  of  2nd  Schmitz  :=0.66% 

Tube  .  , 0000  g. : 

Heated  3  hrs.  at  500°C. 

Heated  litharge  end  \y2  hrs.  at  400°C. 

The  completeness  of  the  dehydration  was  checked  the 
next  morning  by  heating  for  30  minutes  at  650°C.,  and 
holding  the  litharge  end  of  the  tube  at  400°C.  for  one  hour. 
The  increase  in  weight  of  the  Schmitz  tube  was  0.3  mg. 

(b)  Weight  of  Sample  No.  2  of  K2GeF6.  . .  .1.0000  g.  , 
Absorption  of  1st  Schmitz 

Tube 0063  g. : 

Absorption  of  2nd  Schmitz  :=0.67% 

Tube    0004  g.  : 

Heated  2  hrs.  at  600° C. 
Litharge  end  at  400°C.  for  one  hour. 

The  completeness  of  the  dehydration  was  checked  by 
heating  the  sample  one-half  hour  at  600° C.  and  the,lith- 
arge  end  at  400°C.  for  one  hour.  The  increase  in^  weight 
of  the  Schmitz  tube  was  0.1  mg.  •  >..<:a:>;  *>,- 

The  hard  glass  tube  was .  strongly  etched,  showing  de- 
composition took  place.    The  bulb  at  thejten.tra-TiQ-QrQf  ,the 
Schmitz   tube   showed   no    sign   of   etching   during^, 
determinations.   .>,>,*  *j  i 

The  formula  K2GeFG.l/10  H,Q  gives  0,676,%, 
Determination   of   the   Volatility   of   Potass ium^ 
on  Evaporating  a  Water  Solution.  ,  .^:^.?          1 

This  experiment  was  carried  out  as  a  check  upon  losses  in  the 
preparation  of  this  salt,  but  the  results  are  interesting  when  com- 
pared with  those  obtained  from  the  water  determination. 

A  sample  of- potassium  fluogermanate  weighing  0.5156  g.  was 
weighed  in  a  tared  platinum  dish  and  dried  for  1  hr.  on  an  air 
bath  covered  with  asbestos  paper.  After  weighing  the  dish  and 
content,  60  cc.  of  water  was  added.  The  water  was  boiled  until 
solution  was  complete.  The  solution  was  evaporated  to  dryness 
and  the  dish  was  heated  as  before  for  1  hr.  The  weight  of  the 
dish  and  contents  was  exactly  the  same  as  before  solution. 

23 


No  volatilization  of  any  constituent  had  occurred.  Apparently 
decomposition  did  not  occur.  While  the  sample  was  not  the  same 
as  that  used  in  the  water  determinations,  the  mode  of  preparation 
was  very  similar  and  it  undoubtedly  contained  water.  That  the 
water  content  after  evaporation  of  the  solution  should  be  exactly 
the  same  as  before  appears  remarkable,  unless  it  be  water  of 
crystallization  according  to  the  formula  given  above. 

Conclusions  from  determinations  of  water. 

The  potassium  fluogermanate  'after  thorough  drying  still  con- 
tains some  water  which  causes  decrepitation  when  it  is  released. 

The  amount  of  water  retained  appears  practically  constant. 

The  water  is  given  up  by  heating  in  a  current  of  dry  air  at 
about  500°  C. 

On  heating  in  a  closed  crucible  the  water  is  not  given  off  appre- 
ciably until  a  temperature  of  over  500°C.  is  reached. 

Decomposition  begins  in  a  current  of  dry  air  at  about  500°C. 
At  600°C.  the  action  is  very  marked.  Both  glass  and  quartz  are 
strongly  etched. 

Ignition  in  a  crucible  at  a  dull  red  heat  causes  decomposition 
with  no  other  evidence  than  a  continued  loss  in  weight. 

The  water  in  potassium  fluogermanate  cannot  be  determined 
by  the  usual  method  of  drying  in  an  oven  as  it  is  not  released  at 
such  temperatures. 

,The  water  cannot  be  determined  by  the  usual  process  of  absorp- 
tion with  certainty  as  the  temperature  at  which  it  is  released  lies 
too  close  to  the  temperature  of  decomposition. 

The  water  can  be  determined  accurately  by  the  process  of  ab- 
sorption if  the  gases  are  passed  through  pure  lead  oxide  to  absorb 
the  liberated  fluorides. 

Evaporation  of  Potassium  Fluogermanate  with  Sulphuric  Acid. 

Kriiss  and  Nilson1  describe  two  analyses  of  potassium  fluoger- 
manate made  by  evaporating  a  solution  of  the  salt  in  a  platinum 
crucible  with  excess  of  sulphuric  acid,  first  over  a  \vater  bath,  and 
finally  at  a  higher  heat.  Adhering  sulphuric  acid  was  driven  off 
by  repeatedly  heating  with  ammonium  carbonate.  The  results 
show  no  appreciable  loss  indicating  that  germanium  fluoride  is 
not  volatilized  under  such  conditions. 

On  the  other  hand,  Winkler-  describes  four  experiments  showing 
a  loss  of  germanium  by  evaporation  of  the  double  fluoride,  or 


'Her.,  20,   (1887)   1698. 

-J.   Prakt.  Them.,  36,  (1887)   1%. 


24 


germanium  dioxide  and  calcium  fluoride,  with  sulphuric  acid.  In 
one  instance  he  shows  a  loss  of  5.42%  of  germanium  dioxide  by 
heating  potassium  fluogermanat€  with  dilute  sulphuric  acid. 

Evaporation  in  a  Snowdon  Furnace  and  Neutralization  of 
the  Sulphuric  with  Ammonium  Carbonate  or  Hydroxide. 
Five-tenths  gram  of  Sample  No.  2  was  weighed  in  a  plat- 
inum crucible,  10  cc.  of  water  was  added,  and  the  mixture  was 
heated  in  a  Snowdon  furnace.  Dilute  sulphuric  acid  in  slight 
excess  over  the  calculated  amount  was  added,  and  the  solu- 
tion was  evaporated  at  a  temperature  just  below  boiling  until 
sulphuric  anhydride  fumes  were  given  off.  The  temperature 
was  gradually  increased  to  the  capacity  of  the  furnace  and  con- 
tinued until  fumes  were  no  longer  expelled.  After  cooling, 
2  cc.  of  ammonium  carbonate  solution  (1:5)  was  added  and  the 
solution  carefully  evaporated  to  dryness.  This  treatment  was 
repeated  twice  when  the  crucible  was  ignited  and  weighed. 
Evaporation  with  ammonium  carbonate  solution,  ignition,  and 
weighing  were  repeated  but  a  constant  weight  could  not  be 
obtained.  A  flaky  white  residue  remained  which  decrepitated 
so  badly  both  on  heating  and  on  cooling  the  crucible  that  it 
was  thrown  out  even  when  the  crucible  was  covered. 

Five  determinations  were  made  by  this  method  varying  the 
conditions  to  avoid  the  decrepitation.  Two  determinations 
were  lost  by  creeping  or  spurting.  In  one  ammonium  hydrox- 
ide (1  :1)  was  substituted  for  ammonium  carbonate  solution. 
None  of  these  changes,  however,  gave  constant  results.  A 
typical  set  of  data  is  given  below. 

Weight  of  Sample  No.  2 0.5000  g. 

Weight  of  crucible  and  residue  evap- 
orated  three   times    with   ammonium 

carbonate  solution  and  ignited 19.1901  g. 

Ditto,  evaporated  again  with  ammonium 

carbonate   solution  and  ignited 19.1821  g. 

Ditto, 19.1742  g.  i 

Ditto,    19.1732  g.  * 

Ditto, 19.1720  g. 

Evaporation  in  a  Snowdon  Furnace  and  Neutralization 
with  Ammonia  Carried  by  a  Current  of  Air. —  i 

Current  of  Air. — This  was  modified  from  the  device 
used  by  Kruss  and  Moraht1. 


'Ann.   e,   262   (1891)    51. 

25 


The  sample  was  weighed  in  a  platinum  crucible. 
Fifteen  cc.  of  sulphuric  acid  (1  :6)  Was  added  and  the 
mixture  was  heated  in  a  Snowdon  furnace.  Solution 
was  nearly  or  quite  complete.  The  solution  was  evap- 
orated at  this  temperature  (no  formation  of  bubbles 
was  permitted).  When  about  one-half  of  the  liquid 
was  gone,  white  crystals  began  to  form  and  soon  the 
solution  was  filled  with  the  crystalline  mass  giving  a 
jelly  like  consistency.  '  A  shell  formed  over  the  top 
interfering  with  the  evaporation.  Eight  cc.  more  of 
sulphuric  acid  (1 :6)  was  added.  By  means  of  a  little 
agitation  the  solid  was  caused  to  settle  to  the  bottom 
when  evaporation  readily  occurred.  The  latter  was 
continued  until  sulphur  trioxide  fumes  were  given  off 
when  the  temperature  \vas  increased  to  the  full  ca- 
pacity of  the  furnace  and  held  there  until  no  more 
fumes  escaped. 

After  cooling  the  crucible  was  fitted  with  a  perfor- 
ated platinum  cover  bearing  a  bent  glass  tube  held  in 
place  by  a  small  bulb.  Compressed  air  which  was  slow- 
ly bubbled  through  concentrated  ammonium  hydroxide 
solution  was  passed  into, the  crucible.  This  was  con- 
tinued *at  .room  temperature  3^  to  4  hrs.  A  lamp 
bank  was  used  to  control  the  current  as  .previously 
described.  Two  lamps  (about  190°C.)  .was  first  used. 
The  temperature  wras  gradually  increased  by  adding  a 
lamp  to  the  circuit  at  intervals  of  l/2  hr.  until  a  tem- 
perature of  about  600°  was  reached,  the  current  of  air 
saturated  with  ammonia  being  continued  throughout 
the,  process.  Heating  was  maintained  at  the  full  tem- 
perature from  2  to  2~y2  hrs.  The  crucible  was  then 
removed  to  a  triangle  covered  a,s  usual,  and  ignited 
first  with  a  low  flame  and  finally  at  a  dull  red  heat  for 
15  minutes.  It  was  then  cooled  and  weighed.  Treat- 
ment with  ammonia  was  repeated  for  2~y2  to  3  hrs. 
when  the  crucible  was  again  ignited  and  weighed. 

The  residue  was  fairly  tenacious  and  gave  no  de- 
crepitation. No  signs  of  loss  were  detected  through- 
out the  process. 


26 


Data: 

(a)   Weight  of  Sample  No.  2 0.5000  g. 

Weight    of    platinum    crucible    and 
residue  after   1st  treatment  with 

ammonia 19.1931  g. 

Ditto,    after    2nd    treatment    with 

ammonium    19.1931  g. 

Weight  of  crucible 18.6704  g. 


Weight  of  residue .5227  g. 

Calculation  : 

Percentage  of  KoGeF6  in  residue 

(GeO2+K,SO4)  =94.596 
0.5227X0.94596          97r/ 

0.5000   '         "27/l  °f  KaGeF' 

(b)  Weight  of  Sample  No.  2 0.5000  g. 

Weight    of    crucible    and    residue,     1st 

treatment    19.1940  g. 

Weight    of    crucible    and    residue,    2nd 

treatment    -. 19.1934  g. 

Weight    of    crucible    and    residue,    3rd 

treatment    .  IV. ; .  .V. 7 19.1938  g. 

Weight  of  crucible 18.6702  g. 


Weight  of  residue  (2nd  treatment) ...     .5232     g. 
Percentage  of  -K2GeFe=99.36 
Average,  99.32%  of  K2GeF0 

This  gives  for  the  percentage  of  water  0.68  which 
is  an  excellent  agreement  with  that  found. 

Determination  of  Germanium. 

This  was  undertaken  for  the  same  purpose  of  proving  the  purity 
of  the  potassium  fluogermanate.  At  the  same  time  much  informa- 
tion was  obtained  regarding  the  method  of  determining  germanium 
by  precipitation  with  hydrogen  sulphide1. 

Having  proven  that  germanium  is  not  volatilized  by  evapo- 
ration of  potassium  fluogermanate  with  dilute  sulphuric  acid, 
this  method  of  decomposing  the  fluogermanate  was  utilized 
to  determine  the  amount  of  germanium  present. 

HVinkler,  J.   prakt.   Chem.,  34,    (1886),  228. 

27 


The  method  was  as  follows :  Five-tenths  gram  of  potassium 
fluogermanate  was  dissolved  by  boiling  with  25  cc.  of  water 
in  a  platinum  dish.  Seven  and  one-half  cc.  of  sulphuric  acid 
(1  :1)  was  then  added,  a  few  drops  at  a  time,  giving  time  for 
the  escape  of  hydrofluoric  acid.  During  this  addition  the  dish 
was  heated  on  an  air  bath.  The  solution  was  not  allowed  to 
boil.  A  test  by  etching  showed  that  hydrofluoric  acid  was 
being  given  ofT.  The  solution  was  then  evaporated  to  about 
one-half  volume.  A  small  amount  of  granular  white  powder 
separated. 

The  solution  and  precipitate  were  transferred  to  a  500  cc. 
Erlenmeyer  flask  with  water.  The  solution  was  made  approx- 
imately 1 :6  with  sulphuric  acid,  cooled,  and  saturated  with 
hydrogen  sulphide,  the  gas  being  passed  for  about  an  hour. 
The  flask  was  stoppered  and  allowed  to  stand  over  night. 

The  precipitate  was  filtered,  washed  with  sulphuric  acid 
(1:13)  which  had  been  saturated  with  hydrogen  sulphide.  It 
was  then  rinsed  into  a  No.  6  porcelain  crucible.  The  filter 
was  washed  four  times  with  ammonium  hydroxide  by  dripping 
it  over  the  paper.  The  paper  was  burned  in  a  separate  cru- 
cible, taking  care  that  the  ash  did  not  stick  to  the  porcelain. 
The  ash  was  then  added  to  the  remainder  of  the  precipitate. 
The  solution  in  the  crucible  was  evaporated  to  dryness  over 
a  hot  plate  and  concentrated  nitric  acid  was  added  to  convert 
the  residue  to  germanium  dioxide.  Action  here  was  too  vio- 
lent. Nitric  acid  (1:1)  is  better.  The  acid  was  evaporated  off 
and  the  treatment  was  repeated. 

Ammonium  hydroxide  was  added  to  neutralize  adhering 
sulphuric  acid.  It  was  evaporated  off  and  the  residue  was 
ignited  and  weighed  as  germanium  dioxide.  Percentage  of 
germanium  in  germanium  dioxide — 69.38. 

The  evaporation  to  dryness  in  the  crucible  required  much 
care  because  of  danger  of  loss  by  spurting.  Two  determina- 
tions gave  lo\v  results  because  of  this.  The  filtrates  from  these 
two  determinations  were  combined,  saturated  with  hydrogen 
sulphide,  and  allowed  to  stand  several  days.  A  white  floccu- 
lent  precipitate  settled  out  which  was  filtered,  washed,  oxidized 
with  nitric  acid,  and  tested  in  the  spectroscope.  It  gave  a 
strong  test  for  germanium. 

Corrections  were,  therefore,  made  on  the  filtrates  from  the 
last  two  determinations  in  a  similar  manner.  The  precipitates 

28 


were  subjected  to  the  same  treatment  as  the  main  body  of  the 
germanium  disulphide.    The  results  were  as  follows : 


Percentage  of 
Ge-manium  Correction  Corrected  Per- 


Number 
1 

Weight  of 
Sample 

0.5000 

in  First  Pre- 
cipitate 

27.04 

Weight  of 
GeO2 

centage  of 
Germanium 

2 

3 

1.0000 
1.0000 

26.90 
26.88 

0.0042 

0.0036 

27.20 
27.13 

The  percentage  of  germanium  present  calculated  from  the 
formula  allowing  for  the  water  present  as  shown  by  the 
average  of  the  best  determinations  was  27.21.  That  given  by 
calculation  from  the  residue  after  evaporation  with  sulphuric 
acid  was  27.20. 

Conclusions  from  the  Results  of  the  Analysis  of  Potassium 
Fluogermanate. — The  main  purpose  of  this  analysis,  the  proof 
of  the  purity  of  the  potassium  fluogermanate  and  the  conse- 
quent verifications  of  the  method  of  extraction  and  purification 
is  well  established  by:  first,  spectroscopic  test  together  with 
the  absense  of  arsenic  and  the  solubility  of  the  salt ;  second, 
agreement  between  the  determination  of  water,  the  evapora- 
tion with  sulphuric  acid,  and  the  direct  determination  of 
germanium. 

Other  important  facts  established  are  as  follows : 

Separation  of  arsenic  and  germanium  can  be  accomplished 
by  formation  of  potassium  fluogermanate  and  two  recrystal- 
lizations. 

Water  remains  in  the  salt  after  drying  for  several  days  at 
105-1 10°C.  The  water  is  not  driven  off  at  temperatures  below 
500°  C 

A  method  for  the  accurate  determination  of  water  in  potas- 
sium fluogermanate. 

The  constancy  of  the  salt  on  evaporation  with  water,  both 
regarding  volatility  of  its  constituents  and  the  amount  of 
water  present. 

Decomposition  of  the  salt  at  a  dull  red  heat  and  the  tem- 
perature at  which  it  begins  to  decompose  when  heated  in  air. 

Temperature  at  which  decomposition  begins  when  heated  in 
a  current  of  dry  air.  The  amount  of  germanium  volatilized  is 
a  considerable  portion  of  that  present. 

29 


Germanium  is  not  volatilized  by  evaporation  of  potassium 
fluogermanate  with  dilute  sulphuric  acid. 

A  method  for  testing  the  purity  of  potassium  fluogermanate 
by  evaporation  with  sulphuric  acid  and  of  neutralizing  the  sul- 
phuric acid  adhering,  without  the  usual  mechanical  loss. 

The  determination  of  potassium  by  either  the  perchlorate 
or  the  chlorplatinate  methods  gives  erroneous  results  due  to 
the  contamination  with  germanium  dioxide. 

The  determination  of  fluorine  by  precipitation  as  calcium 
fluoride  does  not  give  accurate  results,  apparently  due  to  the 
interference  of  germanium. 

A  direct  method  of  determining  germanium  in  potassium 
fluogermanate. 

The  incomplete  precipitation  of  germanium  by  saturation 
of  the  acid  solution  with  hydrogen  sulphide  and  a  method  of 
correcting  for  the  same. 


30 


DETECTION  OF  GERMANIUM. 


Th.  Richter  seems  to  have  been  the  first  to  subject  this  element 
to  a  blow  pipe  analysis  but  apparently  did  not  suspect  its  presence. 
Later  Penfield1  detected  germanium  in  argyrodite  from  a  new 
source  by  this  means. 

The  method  most  frequently  employed  for  the  detection  and 
identification  of  germanium  has  been  the  formation  of  some  of  its 
principal  compounds,  such  as  the  sulphides,  sulphogermanates,  and 
fluogermanate,  also,  the  element  itself. 

The  spectroscope,  with  either  the  arc  or  spark  spectrum,  was 
employed  for  the  detection  of  the  element  in  new  sources  by 
Urbain2,  Bardet3,  and  Dr.  Burns  of  the  U.  S.  Bureau  of  Standards4. 

Buchanan5  distilled  the  material  with  hydrochloric  acid  in  a 
current  of  chlorine  gas  and  identified  germanium  by  precipitaton 
of  the  white  sulphide  and  by  preparation  of  the  fluogermanate. 

Browning  and  Scott0  modified  the  method  by  using  instead  of 
chlorine  gas  an  oxidizing  agent  such  as  potassium  chlorate,  man- 
ganese dioxide,  potassium  permanganate,  or  potassium  dichromate. 
They  relied  upon  the  precipitation  of  the  white  sulphide  with 
hydrogen  sulphide  for  identification  of  the  element. 

The  author  has  not  been  able  to  tell  with  certainty  the  presence 
of  a  small  amount  of  germanium  in  a  solution  containing  chlorine 
by  means  of  the  precipitation  with  hydrogen  sulphide,  on  account 
of  the  simultaneous  precipitation  of  sulphur.  Even  in  hydro1 
chloric  acid  solution  with  no  chlorine  present  precipitates  were 
obtained  which  certainly  appeared  to  contain  germanium  disul- 
phide,  but  which,  on  oxidizing  with  nitric  acid  and  igniting,  gave  no 
appreciable  residue. 

Spectroscopic  Test. 

Of  all  the  methods  used  for  the  detection  of  germanium,  that 
with  the  spectroscope,  as  described  below,  proved  the  most  reliable. 
It  was  used  throughout  the  work  to  trace  the  presence  of  the 
element  in  the  products  obtained.  Over  300  samples  were  thus 
tested. 


'Am.   J.   Sci.,   (3)  46,   (1893)    107. 

-Compt.  rend.,  149,  (1909)  602. 

•''Compt.  rend.,  157,  (1913)  225. 

4J.  Ind.   Eng.  Chem.,  8,  (1916)  225. 

&J.  Ind.  Eng.  Chem.,  8  (1916),  586. 

°Am.  J.  Sci.,  44,  (1917)  313:  46,  (1918)  663. 


31 


The  method  was  as  follows  :  an  electric  arc  was  prepared  from 
ordinary  electric  light  carbons  using  about  one-quarter  of  a  carbon 
for  each  electrode.  The  sample,  in  the  form  of  a  dry  powder,  was 
placed  on  the  lower  (positive)  carbon.  The  length  of  exposure  was 
controlled  by  a  switch. 

A  Hilger  spectroscope  with  fixed  collimator  and  telescope  was 
used,  also  a  photographic  attachment. 

Exposure  was  made  for  about  three  seconds,  the  time  depending 
upon  the  volatility  of  the  elements  present.  Readings  were  made 
directly  from  the  negative  by  Mr.  R.  W.  G.  Wyckoff.  The  arc 
always  contained  iron,  calcium,  and  sodium,  generally  also  barium, 
but  these  did  not  interfere  in  most  of  the  tests.  A  comparison  of 
the  intensity  of  these  lines  with  those  from  the  sample  was  often 
made  by  taking  a  photograph  of  the  arc  itself.  As  a  glass  prism 
was  used  only  the  lines  in  the  visible  spectrum  were  obtained.  In 
fact,  only  one  line  was  prominent  enough  to  be  of  service.  This 
line  is  of  slightly  greater  wave  length  than  the  third  of  the  zinc 
triplet  (4680.4  A  .U.)  It  practically  coincides  with  the  edge  of 
fourth  band  for  carbon  in  the  blue  (about  4684.  A.  U.) 

The  test  was  found  to  have  certain  limitations.  Positive  results 
were  very  certain  but  negative  results  and  evidence  of  traces  were 
often  unreliable.  The  latter  was  mainly  due  to  the  coincidence  of 
the  principal  germanium  line  with  a  carbon  band. 

In  general,  volatile  substances  often  caused  failure,  probably  by 
cooling  the  arc  below  the  point  where  germanium  is  volatilized. 
This  was  partially  overcome  by  lengthening  the  time  of  exposure. 
It  was  often  possible  to  drive  off  the  volatile  compound  by  ignition. 
The  elements  which  caused  this  effect  were  arsenic,  silver,  mag- 
nesium, molybdenum,  and  potassium.  Ammonium  hydroxide  was 
first  used  for  neutralizing  the  sulphuric  acid  adhering  to  the  sul- 
phide precipitate.  It  was  found  to  enhance  the  carbon  band,  which 
coincides  with  the  germanium  line,  rendering  the  readings  unreliable 
for  small  amounts  of  germanium.  Sodium  hydroxide  was  tried 
but  the  spectrum  was  so  brilliant  that  it  covered  the  germanium 
line.  Potassium  hydroxide  was  then  used  but  apparently  suppressed 
the  line  by  its  volatility.  The  sulphides,  especially,  when  much  ar- 
senic was  present,  gave  a  similar  effect.  This  was  largely  obviated 
by  oxidizing  the  sulphides  with  nitric  acid  and  igniting.  In  some 
cases  adhering  sulphuric  acid  was  neutralized  with  ammonium 
hydroxide,  evaporated  and  the  residue  ignited.  This  prevented  the 
effect  of  the  ammonium  salt. 

32 


Lead,  zinc,  cadmium,  tin,  copper,  and  barium,  in  the  amounts  usu- 
ally found,  caused  no  interference.  However,  residues  obtained  by 
evaporation  of  solutions  containing  large  amounts  of  any  of  these 
salts  usually  failed  to  give  the  germanium  line,  even  when  an 
appreciable  quantity  of  the  element  was  present. 

When  the  calcium  compound  was  the  main  constituent  present, 
the  spectrum  gave  a  line  which  could  not  be  readily  distinguished 
from  that  of  germanium. 

The  Molybdate  Test. — To  determine  whether  germanium 
would  interfere  with  this  test,  pure  germanium  materials  were 
used,  following  the  directions  given  in  Dennis  and  Whittelsey's 
Qualitative  Analysis,  page  33. 

Germanium  dioxide,  from  a  quantitative  determination 
of  germanium  in  pure  potassium  fluorgermanate,  was  dis- 
solved by  boiling  with  water  until  the  saturated 
solution  was  obtained.  This  solution  was  filtered, 
acidified  with  nitric  acid,  and  added  to  a  solution  of  ammo- 
nium molybdate.  The  mixture  was  warmed  on  a  water 
bath  to  70° C.  A  copious  yellow  precipitate  resulted, 
indistinguishable  from  that  given  by  arsenic. 

Pure  germanium  dioxide  was  boiled  with  potassium 
hydroxide  solution  (1 :10).  The  solution  was  filtered,  acidi- 
fied with  nitric  acid,  and  tested  as  above  described.  A 
copious  yellow  precipitate  of  similar  appearance  resulted. 
The  conclusions  from  these  experiments  were,  that  ger- 
manium under  similar  conditions  forms  a  compound  with 
ammonium  molybdate  that  cannot  easily  be  distinguished 
from  that  given  by  arsenic  and  phosphorus.  In  these 
materials,  phosphoric  acid  was  excluded  by  the  method  of 
preparation,  and  arsenic  had  been  repeatedly  proven  absent. 
The  spectroscopic  test  is  useless  in  the  presence  of 
molybdenum. 

The  molybdate  test  evidently  cannot  be  used  in  the 
presence  of  germanium  as  a  test  for  arsenic. 

It  appeared  promising  as  a  test  for  germanium  when 
arsenic  was  excluded,  as  in  the  distillation  method,  or 
perhaps  on  the  precipitate  from  the  reduction  of  ger- 
manium with  zinc  and  sulphuric  acid. 


33 


PREPARATION  OF  PURE  GERMANIUM  DIOXIDE. 


Germanium  dioxide  proved  to  be  the  most  convenient  starting: 
point  for  much  of  the  study  of  the  chemistry  of  germanium,  es- 
pecially from  the  analytical  view  point.  Its  preparation  in  a  high 
state  of  purity  is,  therefore,  important. 

Winkler1  recommends  hydrolysis  of  the  chloride  as  giving  the 
purest  product  but  states  that  the  yield  is  not  good.  He  also 
mentions  its  preparation  by  ignition  of  the  element  in  oxygen  by 
roasting  germanium  disulphide  and  by  heating  the  latter  with 
sulphuric  acid. 

Preparation   from   Potassium  Fluogermanate. 

Evaporation  with  .Sulphuric  Acid  and  Precipitation  with 
Hydrogen  Sulphide. — It  was  desired  to  obtain  germanium  di- 
oxide from  the  potassium  fluogermanate  already  prepared 
whose  purity  had  been  established. 

Winkler  states2  that  potassium  fluogermanate  can  be  de- 
composed and  the  fluorine  eliminated  by  evaporation  with 
sulphuric  acid  but  the  procedure  for  large  quantities  is  not  to 
be  recommended  because  of  volatilization  of  germanium 
fluoride. 

Since  the  author  had  proven  that  evaporation  of  this  double 
salt  with  dilute  sulphuric  acid  leads  to  no  loss  of  germanium, 
the  method  was  tried  for  preparation  of  pure  germanium 
dioxide. 

Sixteen  grams  of  potassium  fluogermanate  was  dissolved 
by  boiling  it  with  700  cc.  of  water  in  a  platinum  dish.  To  this 
was  slowly  added  60  cc.  of  sulphuric  acid  (1 :1).  The  mixture 
was  evaporated  to  one-half  its  volume.  It  was  transferred  to 
a  2  1.  Erlenmeyer  flask  with  water  and  made  up  to  a  volume  of 
1540  cc.  Five  hundred  and  sixty  cc.  of  sulphuric  acid  (1:1) 
was  added,  giving  2100  cc.  of  solution  with  a  concentration 
of  acid  of  1 :6. 

Hydrogen  sulphide  was  passed  from  the  Kipp's  generator 
until  precipitation  appeared  complete.  The  flask  was  stoppered 
and  allowed  to  stand  over  night.  The  precipitate  was  fil- 

'J.   prakt.  Chem.,  34,   (1886)   211. 
-J.  prakt.  Chem.,  36,   (1887)  186. 

34 


tered  and  washed  with  sulphuric  acid  (1:9)  which  had  been 
saturated, with  hydrogen  sulphide. 

The  sulphide  was  rinsed  into  a  weighed  porcelain  evaporat- 
ing dish  and  the  adhering  precipitate  was  dissolved  with  am- 
monium hydroxide  (1:1).  The  solution  was  evaporated  to 
one-half  volume,  nitric  acid  (1:1)  was  added,  and  evaporated 
off.  Treatment  with  nitric  acid  (concentrated)  was  repeated 
until  oxidation  appeared  complete.  The  residue  was  then 
evaporated  with  ammonium  hydroxide,  ignited,  and  weighed. 
Treatment  with  ammonium  hydroxide  was  repeated.  A  cor- 
rection for  solubility  of  germanium  disulphide  was  made  as 
usual. 

Data: 

Weight  of  GeO,  in  the  K2GeF6 6.275  g. 

Weight  of  GeO,  found '. 6.060  g. 

A  slight  spattering  occurred  which  would  account  for  part 
or  all  of  the  difference.  The  result  shows  that  in  as  large 
quantities  as  could  be  handled  the  loss  by  volatilization  is  in- 
appreciable, and  probably  practically  none  occurs.  Several 
other  such  preparations  pointed  to  the  same  conclusion  but 
the  data  were  not  so  definite.  Attention  should  be  called  to 
the  fact  that  the  conditions  for  evaporation  were  a  dilute 
solution  and  an  addition  of  sulphuric  acid,  a  few  drops  at  a 
time. 


35 


THE  DETERMINATION  OF  GERMANIUM 


No  satisfactory  method  for  the  separation  of  germanium  from 
the  accompanying  elements  and  determination  of  the  germanium 
has  yet  been  described.  Winkler1  used  a  method  of  deter- 
mination of  germanium  in  the  argyrodite  ore  based  on  the  sepa- 
ration with  sodium  sulphide  and  separation  of  arsenic  by  fractional 
precipitation,  finally  precipitating  the  germanium  as  the  disulphide 
and  converting  the  latter  to  dioxide.  The  results  could  be  only 
approximate. 

Penfield  determined  germanium  in  argyrodite2  and  later  in 
canfieldite3  by  decomposing  the  mineral  with  nitric  acid,  separat- 
ing the  silver  with  ammonium  thiocyanate,  and  after  a  further 
purification  with  ammonium  sulphide,  obtained  the  germanium  as 
the  dioxide  by  evaporating  the  solution  with  nitre  acid.  Arsenic 
appears  to  have  been  absent. 

The  methods  here  described  were  based  on  that  proposed  by 
Winkler  of  precipitating  germanium  as  germanium  disulphide  and 
converting  to  the  dioxide,  the  conditions  for  which,  however,  had 
not  been  well  described. 

Determination  of  Germanium  in  Pure  Solutions. 

Solution  of  Germanium  Dioxide  in  Water. — Two  and 
one-half  grams  of  pure  germanium  dioxide  was  boiled 
with  2  1.  of  water  for  about  2  hours.  The  solution  was 
filtered  twice  but  was  still  slightly  turbid.  On  standing 
2  days,  a  slight  amount  of  solid  settled  out.  Four  cc.  of 
ammonium  hydroxide  was  added  but  the  solution  was  still 
turbid.  Eight  cc.  of  nitric  acid  was  added  and  the  solu- 
tion was  again  boiled.  This  gave  a  clear  solution  which 
was  permanent  until  completely  used. 

The  solution  was  standardized  by  evaporating  50  cc.  in  a 
platinum  dish  over  a  water  bath,  igniting  the  residue  over 
a  triple  burner,  cooling  in  a  desiccator,  and  weighing. 
The  results  were  as  follows : 

50  cc.  Germanium  Dioxide  Solution^  .0618  g.  GeO2 
50  cc.  Germanium  Dioxide  Solution^  .0614  g.  GeO., 


JJ.  prakt.  Chem.,  34  (1886)  228. 
"Am.  J.  Sci.,  (3)  46,  (1893)  110. 
"Am.  J.  Sci.,  (3)  47,  (1894)  452. 


36 


A  second  solution  was  prepared  in  a  similar  manner  using 
3  g.  germanium  dioxide,  2  1.  of  water,  *5cc.  ammonium 
hydroxide,  and  8  cc.  nitric  acid.  In  standardizing  the  so- 
lution, it  was  found  that  great  care  was  necessary  in 
handling  the  ignited  residue  as  it  was  easily  lost  in  slight 
currents  of  air.  Two  determinations  were  lost  through 
the  rush  of  air  on  opening  the  desiccator.  By  covering  the 
dish  with  a  watch  glass  and  carefully  opening  the  desic- 
cator, this  was  avoided  and  very  constant  results  were 
obtained.  Four  determinations  were  as  follows  : 

40  cc.  Germanium  Dioxide  Solution  gave  0.0588  g.  GeO2 
40  cc.  Germanium  Dioxide  Solution  gave  0.0588  g.  GeCX 
40  cc.  Germanium  Dioxide  Solution  gave  0.0588  g.  GeCX 
40  cc.  Germanium  Dioxide  Solution  gave  0.0587  g.  GeCX 

A  Study  of  Conditions  for  the  Determination  of  Germanium 
by  Precipitation  as  Germanium  Disulphide. 

(1).  In  Sulphuric  Acid  Solution. — Method.  An  acid 
solution  of  germanium  dioxide  was  prepared  having  a 
volume  of  about  150  cc.  and  the  proportions  indicated  be- 
low. The  solution  cooled  to  room  temperature  was  treated 
in  an  Erlenmeyer  flask  with  hydrogen  sulphide,  the  gas 
being  passed  from  45  min.  to  1  hr.,  and  until  most  of  the 
germanium  disulphide  had  settled  out.  The  flask  was 
stoppered  and  allowed  to  stand  over  night.  The  precipi- 
tate was  filtered  and  washed  as  indicated  below.  The 
treatment  of  this  precipitate  was  so  varied  that  each  case 
will  be  described  separately,  but  in  all  cases  it  was  con- 
verted to  the  dioxide,  adhering  sulphuric  acid  was  removed 
by  use  of  ammonium  hydroxide  or  carbonate,  and  the  resi- 
due was  weighed  as  germanium  dioxide. 

The  filtrate  from  germanium  disulphide  had  been  shown 
to  contain  germanium.  It  was  saturated  with  dydrogen  sul- 
phide and  the  flask  was  allowed  to  stand,  stoppered,  for 
at  least  two  days,  when  a  nearly  white  precipitate  settled 
out.  This  was  filtered,  washed,  converted  to  the  dioxide, 
and  weighed.  The  results  were  as  follows : 


37 


Data: 

Determinations  of  Germanium  in  Pure  Solutions. 


Ratio 

Washed  with 

Weight  of  GeOi  found 

HjS04 

p_r» 

+rt 

I  Vr  cent 

No. 

LfCw  I 

Present 

to 
other 

alcohol 

grams 

liquids 
by 

by 
weight 

Acid  solution 

Alcohol 

First  pre- 
cipitate 

Correction 

Total 

volume 

gr. 

gr. 

gr. 

| 

0.1492 

1:10 

None... 

H2S04  (1:13). 

None  

0  1231 

+H2S 

2  

0  1492 

1:6 

None.  .  . 

H2S04  (1:13). 

Until  free  from 

0  1475 

00018 

.1492 

3... 

0  1492 

1:6 

« 

h       « 

4« 

0  1503 

4  

0  0616 

1:6 

« 

HzSO*  (1*9) 

" 

0  0602 

6!66i3 

ooeis 

+H2S  ' 

5  

00616 

1:6 

" 

" 

" 

0  0600 

0  0009 

0  0609 

6... 

00616 

1:6 

.< 

M 

25cc... 

0  0592 

7  

00616 

1:6 

" 

" 

lOOcc  

0  0576 

Voiatili 

zed.' 

g 

00616 

1:6 

,< 

JU 

300cc  

e  0601 

Voiatili 

zed. 

9 

0  0616 

1:6 

(( 

Washing  solu- 

Until   H2S04 

0  0620 

tion. 

was  gone. 

10  

0  0616 

1:6 

14  9 

*' 

25cc.  

0  0602 

00016 

0  0618 

11  

0  0616 

1:6 

14  9 

" 

« 

0.0589 

0  0015 

0.0604 

12  

00616 

1:6 

14  9 

M 

H 

0.0600 

0  0008 

0  0608 

13 

00616 

1:8.8 

19.8 

„ 

u 

0  0595 

00016 

0  0611 

14 

0.0616 

1:11.6 

25 

« 

St^ftj 

0  0573 

0.0032 

0  0605 

Explanations : 

No.  1.  This  experiment  was  made  to  determine  whether  a  more 
dilute  sulphuric  acid  solution  would  give  a  more  or  less  complete 
precipitation  of  germanium.  The  precipitate  was  rinsed  into 
a  No.  6  porcelain  crucible  with  a  jet  of  water.  Ammonium  hydrox- 
ide (1:1)  was  dripped  over  the  filter  (about  5  cc.).  The  filter  was 
burned  separately  and  the  ash  added  to  the  main  precipitate.  The 
contents  of  the  crucible  was  evaporated  to  one-half  volume  over 
an  air  bath.  Five  cc.  HNO3  (1 :1)  was  added  and  evaporation  was 
continued  nearly  to  dryness.  Five  cc.  of  concentrated  nitric  acid 
was  then  added  and  the  solution  was  again  evaporated  to  dryness. 
The  residue  was  ignited  over  a  Bunsen  burner.  Ammonium 
hydroxide  was  added  and  evaporated  off.  The  crucible  was  again 
ignited  and  weighed.  Treatment  with  ammonium  hydroxide  and 
ignition  were  repeated  to  constant  weight.  The  result  shows  a 
very  incomplete  precipitation  in  sulphuric  acid  solution  of  con- 
centraton  1 :10. 

No.  2.  This  differed  from  No.  1  in  that  the  precipitate  after 
the  washing  with  sulphuric  acid  solution  was  washed  with  alcohol 


38 


until  free  from  sulphuric  acid.  The  purpose  was  to  prevent  char- 
ring when  the  precipitate  was  dried  so  that  it  could  be  removed 
from  the  filter  and  the  latter  burned  separately.  The  precipitate 
was  evaporated  with  nitric  acid  in  a  No.  00  porcelain  dish  and  the 
moist  residue  was  transferred  to  a  No.  7  porcelain  crucible.  The 
procedure  in  No.  1  was  better  in  this  respect. 

No.  3.  The  precipitate  and  filter  were  transferred  to  a  No.  6 
porcelain  crucible  and  5  cc.  of  nitric  acid  acid  (1:1)  was  added.  The 
solution  was  evaporated  to  dryness,  which  oxidized  the  germanium 
disulphide  and  disintegrated  the  filter.  Nitric  acid  was  again 
added  and  evaporated  off.  The  carbonaceous  matter  was  burned 
off  in  the  open  crucible.  The  residue  was  again  treated  with  nitric 
acid,  evaporated,  ignited,  and  weighed.  The  residue  was  treated 
wth  ammonium  hydroxide  and  ignited,  as  described  above,  to  a 
constant  weight.  In  spite  of  the  constant  weight  indicating  no 
sulphuric  acid  present  the  result  was  high.  Two  out  of  three 
other  determinations  by  this  treatment  of  the  precipitate  gave 
high  results. 

Nos.  4  and  5  were  a  test  of  the  direct  ignition  of  filter  and  pre- 
cipitate. The  wet  filter  was  transferred  to  a  No.  7  porcelain  cru- 
cible and  dried  over  a  low  flame  with  the  cover  on.  The  cover 
was  removed  and  the  filter  burned  using  about  a  half  flame  of  a 
Bunsen  burner.  A  hard  black  mass  resulted  which  was  crushed  in 
the  crucible  with  a  glass  rod,  and  then  ignited  until  white.  No.  5 
did  not  burn  white  and  was,  therefore,  evaporated  with  concen- 
trated nitric  acid  after  which  a  white  residue  was  easily  obtained. 
Ammonium  hydroxide  was  added,  evaporated,  and  the  crucible  was 
again  ignited.  A  constant  weight  was  readily  obtained.  The 
correction  was  made  by  burning  filter  and  precipitate  in  the  cru- 
cible, with  the  main  body  of  germanium  dioxide. 

Nos.  6,  7,  and  8  were  made  to  test  the  use  of  alcohol  for  removing 
sulphuric  acid  from  filter  and  precipitate.  The  purpose  in  the  use 
of  alcohol  was  to  enable  the  drying  of  the  precipitate  so  that  it 
could  be  removed  from  the  filter  and  the  latter  burned  separately. 

The  filter  and  precipitate  were  dried  in  the  electric  oven.  The 
precipitate  was  removed  to  a  watch  glass  by  means  of  a  camels 
hair  brush.  The  dry  germanium  disulphide  adhered  to  the  brush 
badly  so  that  mechanical  loss  probably  occurred  in  the  first  two 
determinations.  In  No.  6  the  filter  slightly  charred  and  was  brittle. 
The  other  two  were  unsatisfactory. 

The  corrections  were   made  by  treating  the  precipitate   in   the 

39 


same  way  as  the  main  portion,  but  the  filter  was  burned  in  the 
same  crucible  with  the  germanium  dioxide  previously  formed.  The 
crucible  was  covered  during  the  drying  and  the  cover  was  left  on 
too  long  resulting  in  volatilization.  In  No.  6  the  crucible  cracked 
giving  an  uncertain  result. 

No.  9  was  a  test  of  the  utility  of  a  washing  solution  which  had 
been  used  for  lead  sulphate.  After  washing  the  precipitate  with 
this  solution  it  was  washed  with  alcohol  until  the  washings  gave 
no  test  with  barium  chloride.  The  precipitates  from  the  first  pre- 
cipitation and  the  correction  were  treated  together  by  the  method 
described  under  No.  1.  Ammonium  carbonate  was  used  instead  of 
ammonium  hydroxide  for  removing  adhering  sulphuric  acid. 

The  washing  solution  consisted  of  740  cc.  of  water,  250  cc.  alco- 
hol, and  10  cc.  sulphuric  acid.  In  later  experiments  this  solution 
was  saturated  with  hydrogen  sulphide  and  filtered.  A  test  of  the 
solubility  of  germanium  disulphide  in  this  solution  was  made  by 
mixing  the  two  in  an  Erlenmeyer  flask,  with  frequent  shaking 
during  a  period  of  several  hours,  and  then  allowing  the  flask  to 
stand  stoppered  over  night.  The  solution  was  filtered  until  clear. 
One  hundred  cc.  of  the  filtrate  wras  evaporated  in  a  platinum  dish 
over  a  water  bath  and  the  sulphuric  acid  was  expelled  by  heating 
over  an  air  bath.  The  dish  was  then  ignited  and  weighed.  The 
residue  was  evaporated  with  hydrochloric  and  sulphuric  acids,  and 
the  dish  again  ignited  and  weighed.  This  was  repeated  until-  a 
constant  weight  was  obtained.  No  loss  in  weight  was  detected  by 
the  evaporation  with  hydrochloric  acid,  showing  no  appreciable 
solution  of  germanium  disulphide  in  the  washing  solution. 

Nos.  10, 11,  12,  13,  and  14  were  a  study  of  the  completeness  of  the 
precipitation  of  germanium  disulphide  in  solutions  containing  alco- 
hol, in  an  effort  to  avoid  the  necessity  for  making  the  correction. 
The  method  varied  from  No.  9  only  in  using  the  washing  solution 
saturated  with  hydrogen  sulphide  and  in  the  treatment  of  the 
precipitate.  In  No.  10  the  precipitate  was  dried  and  separated  from 
the  filter.  In  No.  12  the  wet  filter  was  burned  directly.  In  Nos.  11, 
13,  and  14  the  precipitate  was  rinsed  into  a  No.  00  porcelain  evap- 
orating dish  with  ammonium  hydroxide  (1:1).  The  solution  was 
•evaporated  to  one-half  volume,  5  cc.  of  nitric  acid  (1 :1)  was  added, 
and  evaporation  continued  to  moist  dryness.  A  little  hot  water 
was  added  and  the  contents  of  the  dish  were  transferred  to  a  No.  7 
porcelain  crucible.  The  solution  was  evaporated  to  dryness  and 


40 


the  crucible  was  ignited  and  weighed.     Dry  ammonium  carbonate 
was  added  and  the  crucible  was  ignited  and  weighed. 

The  filtrates  in  the  last  five  determinations  were  clear  until  the 
alcohol  was  added,  when  a  fine  white  precipitate,  like  that  of  pre- 
cipitated sulphur  formed.  In  order  to  determine  whether  this  was 
due  to  dissolved  germanium  disulphide,  the  precipitate  from  the 
five  determinations,  were  filtered  on  the  same  filter,  washed  with 
washing  solution  and  ignited  directly.  The  weight  obtained  was 
0.2  mg.  which  was  no  more  than  that  given  by  blank  determinations 
of  the  filter  paper. 

CONCLUSIONS.  A  sulphuric  acid  solution  of  concentration  1 :10 
gives  incomplete  precipitation  of  germanium  disulphide.  With  a 
concentration  of  1  :6,  it  is  nearly  complete  but  a  correction  is 
necessary. 

Alcohol  in  the  solution  in  which  germanium  disulphide  is  pre- 
cipitated does  not  avoid  the  correction.  It  seems  to  make  the 
precpitation  a  little  more  complete,  but  the  effect  is  not  sufficient 
to  warrant  its  use.  As  alcohol  is  increased  and  sulphuric  acid 
decreased  precipitation  is  less  complete. 

Alcohol  can  be  used  to  wash  out  the  sulphuric  acid  from  the 
precipitate  as  it  does  not  dissolve  germanium  disulphide  appre- 
ciably. The  precipitate  and  filter  can  then  be  dried  in  an  oven 
without  charring  the  latter. 

The  washing  solution  above  described  appears  very  satisfactory 
for  washing  the  precipitate.  It  is  doubtful  whether  saturation 
with  hydrogen  sulphide  is  necessary.  If  not,  it  would  be  more 
pleasant  to  use. 

The  precipitate  after  washing  with  alcohol  and  drying  can  be 
transferred  to  a  watch  glass  and  the  filter  burned  separately.  The 
procedure  is  somewhat  objectionable  on  account  of  the  powdery 
character  of  dried  germanium  disulphide.  Nevertheless,  it  is  more 
simple  than  Winkler's  method  of  handling  the  precipitate  and  gives 
as  accurate  results. 

Evaporation  of  filter  and  precipitate  with  nitric  acid  and  ignition 
of  the  residue  seems  to  lead  to  high  results  for  an  unknown  reason. 
The  procedure  possesses  little  advantage  and  is  not  to  be  recom- 
mended. 

Direct  ignition  of  the  wet  filter  gives  good  results  and  is  by  far 
the  simplest  method.    An  open  crucible  must,  however,  be  used. 
The  Final  Method. 

The  method  a'S  finally  worked  out  is  as  follows :  the  germanium 

41 


solution,  contained  in  a  500  cc.  Erlenmeyer  flask,  is  made  up  to  a 
volume  of  175  cc.  with  a  concentration  of  sulphuric  acid  of  1 :6. 
A  rapid  stream  of  hydrogen  sulphide  is  passed  through  the  solu- 
tion for  at  least  45  min.  and  until  most  of  the  germanium  disulphide 
has  settled  out.  The  flask  is  stoppered  and  allowed  to  stand  over 
night.  The  precipitate  is  filtered  and  washed  with  washing  solu- 
tion (740  cc.  water,  250  cc.  alcohol,  10  cc.  sulphuric  acid,  saturated 
with  hydrogen  sulphide).  The  filter  with  precipitate  is  trans- 
ferred to  a  No.  7  porcelain  crucible,  dried,  and  then  charred  over  a 
low  flame  (the  cover  having  been  removed)  until  a  small  black 
mass  is  obtained,  or,  when  only  a  small  amount  of  germanium  is 
present,  until  the  carbon  is  burned  off.  Nitric  acid  is  added  and 
the  crucible  is  covered  with  a  small  watch  glass.  The  crucible  is 
heated  gently  until  violent  action  is  over  when  the  watch  glass  is 
removed,  rinsed  with  a  little  nitric  acid,  and  the  contents  of  the 
crucible  are  evaporated  to  dryness.  The  residue  is  crushed  by 
means  of  a  glass  r<5d  as  soon  as  the  crucible  is  cooled.  It  is  then 
ignited  over  a  Bunsen  flame  until  white,  cooled,  and  weighed. 
Ammonium  carbonate  is  added  and  the  crucible  is  ignited  gently 
Avith  the  cover  on.  When  the  ammonium  carbonate  is  gone  the 
crucible  is  again  ignited  and  weighed.  The  treatment  is  repeated 
until  a  constant  weight  is  obtained. 

A  correction  for  the  solubility  of  germanium  disulphide  in  the 
filtrate  is  necessary.  It  is  made  by  saturating  the  filtrate  contained 
in  an  Erlenmeyer  flask  with  hydrogen  sulphide,  stoppering  the 
flask,  and  allowing  it  to  stand  at  least  two  days.  A  white  precipi- 
tate composed  largely  of  sulphur  settles  out.  This  is  filtered  and 
treated  as  described  above.  Both  the  main  precipitate  and  the 
correction  may  conveniently  be  treated  together  in  the  same  cru- 
cible, thus  avoiding  several  operations. 

In  precipitating  germanium  disulphide,  it  is  probable  that  the 
volume  can  vary  through  rather  wide  limits,  but  the  concentration 
of  the  acid  cannot  vary  much  from  that  used. 

A  rapid  and  continuous  stream  of  hydrogen  sulphide  seems  to 
be  necessary.  A  few  times  when  the  generator  worked  badly  and 
the  current  was  intermittent,  the  precipitation  wras  incomplete. 

In  igniting  the  precipitate  and  filter,  volatilization  seems  to  occur 
if  the  cover  is  left  on  the  crucible,  as  a  low  result  is  obtained  and 
a  black  sublimate  forms  on  the  cover  and  sides  of  the  crucible  which 
does  not  burn  off  readily.  The  composition  of  this  sublimate  is 
uncertain  as  it  does  not  burn  white  as  readily  as  would  germanium. 

42 


In  an  open  crucible  no  evidence  of  volatilization  is  detected.  The 
filter  chars  to  a  hard  black  mass  when  much  germanium  is  present. 
The  mass  is  rather  difficult  to  crush  with  a  glass  rod  without  loss 
and  burns  white  very  slowly.  After  treatment  with  nitric  acid, 
the  residue  is  easily  crushed  and  quickly  burns  white.  If  crushed 
immediately  after  drying  it  does  not  stick  to  a  glass  rod  or  brush 
but  it  is  hygroscopic  and  causes  trouble  if  allowed  to  stand.  Care 
should  be  exercised  that  all  of  the  carbon  is  burned  off  as  it  may, 
if  present,  cause  loss  by  volatilization.  If  its  presence  is  suspected 
the  treatment  with  nitric  acid  and  ignition  in  an  open  crucible 
should  be  repeated. 

The  use  of  a  watch  glass,  in  the  nitric  acid  treatment,  may  or 
may  not  be  necessary,  according  to  the  amount  of  sulphur  still 
remaining  in  the  residue.  If  much  be  present,  the  action  is  so 
violent  that  there  may  be  danger  of  loss  from  bursting  bubbles, 
although  none  was  positively  detected.  Use  of  dilute  nitric  acid 
(1 :1)  would  probably  avoid  this  difficulty. 

The  residue  thus  treated  shows  little  tendency  to  adsorb  sul- 
phuric acid.  In  many  of  the  determinations  the  free  acid  was 
expelled  on  the  first  ignition. 

Ignition  with  dry  ammonium  carbonate  was  found  much  more 
convenient  than  ammonium  hydroxide  for  removing  adsorbed  acid 
and  just  as  efficient.  However,  the  treatment  rarely  caused  the 
residue,  obtained  from  direct  ignition  of  the  precipitate,  to  show 
appreciable  loss.  It  is  doubtful  whether  the  treatment  for  ad- 
sorbed sulphuric  acid  is  necessary  for  such  residues. 


43 


DETERMINATION  OF  GERMANIUM  IN  THE  GERMANIUM 

CONCENTRATES 


The  apparatus  used  is  shown  in  the  figure : 


A.  Connection  to  hood. 

B.  Filter  flasks  containing   100  cc.   water.     The   flask  was   cooled  in   ice   water. 

C.  Rubber   connections. 

D.  Corks. 

E.  Spiral  condenser. 

F.  Vigreux  tube   sealed  to  distilling   flask. 

G.  Distilling   flask. 
H.  Thermometer. 

I.  Separatory  funnel. 

J.  Muencke  gas  wash  bottle. 

K.  Current   of   chlorine   gas   from    a   cylinder. 

44 


Method.  Twenty  grams  of  germanium  concentrates  was 
weighed  in  a  small  crystallizing  dish  and  transferred  to  the  dis- 
tilling flask  using  a  short  stemmed  funnel  and  a  platinum  rod. 
Fifty  cc.  of  a  solution  continuing  5  g.  of  potassium  hydroxide  was 
poured  through  the  funnel  washing  down  part  of  the  adhering 
powder. 

The  distilling  flask  was  replaced  in  the  apparatus  and  a  stream 
of  chlorine  gas  was  bubbled  through  the  solution.  The  flask  was 
heated  over  an  air  bath.  Chlorination  was  continued  until  the 
temperature  rose  nearly  to  the  boiling  point,  the  flask  being- 
shaken  occasionally  to  secure  complete  oxidation.  The  color  of 
the  mixture  changed  to  a  chocolate.  About  20  min.  were  required 
for  the  chlorination. 

The  dish  in  which  the  concentrates  were  weighed,  the  platinum 
wire,  and  the  funnel  were  rinsed  with  80  cc.  of  hydrochloric  acid. 
The  acid  was  then  added  to  the  separatory  funnel  of  the  apparatus 
and  run  in  a  slow  stream  into  the  distilling  flask,  care  being  taken 
that  the  evolution  of  gas  was  not  so  rapid  as  to  endanger  com- 
plete absorption  of  the  germanium  chloride  in  the  receiving  flask. 
About  10  min.  were  used  for  this  addition.  The  burner  was  re- 
moved during  this  process  but  the  chlorine  was  not  interrupted. 

Heating  was  continued  over  the  air  bath  until  the  contents  of 
the  flask  boiled  vigorously,  then  over  a  wire  gauze  covered  with 
asbestos  paper.  Distillation  was  continued  until  the  volume  was 
reduced  to  the  original  volume  of  the  potassium  hydroxide  solu- 
tion. The  burner  was  removed,  the  chlorine  delivery  tube  discon- 
nected and  the  receiving  flask  replaced  by  a  similar  one.  The  first 
flask  was  labelled  "Distillate  I". 

The  chlorine  was  again  passed.  Fifty  cc.  of  hydrochloric  was 
added  to  the  distilling  flask  and  the  solution  was  again  distilled  to 
the  original  volume.  This  process  was  repeated.  The  second 
receiving  flask  was  labeled  Distillate  II;  the  third,  Distillate  III; 
the  small  flask,  used  to  catch  any  germanium  chloride  that  might 
be  carried  over  from  the  receiving  flask,  was  labelled  "Safety 
Flask."  To  the  latter  was  added  25  cc.  hydrochloric  acid.  Hydro- 
gen sulphide  was  passed  through  these  flasks  from  the  Kipp  gen- 
erator for  at  least  an  hour.  Precipitation  seemed  to  be  complete. 
The  flasks  were  stoppered  and  allowed  to  stand  over  night. 

The  precipitates  were  filtered  and  washed  with  the  washing 
solution,  before  described,  until  free  from  chloride.  The  test  was 
made  by  boiling  about  15  cc.  of  washings  until  hydrogen  sulphide 

45 


and  most  of  the  alcohol  was  gone,  diluting  with  water,  and  adding 
silver  nitrate  solution.  About  the  usual  amount  of  washing  was 
required. 

The  precipitates  were  ignited  directly  to  form  germanium  dioxide 
in  the  manner  previously  discussed.  (See  "Determinaton  of  Ger- 
manium", page  41,  Final  Method).  To  the  residue  in  the  crucible 
was  added  a  few  drops  of  sulphuric  acid  (1:1),  then  two-thirds  of 
a  crucible  full  of  hydrochloric  acid.  The  solution  was  evaporated  to 
sulphur  dioxide  fumes.  Hydrochloric  acid  was  again  added  and 
evaporation  was  continued  until  sulphur  dioxide  fumes  were  driven 
off.  The  crucible  was  ignited,  ammonium  carbonate  was  added, 
and  then  ignition  was  continued,  gently  at  first,  finally  for  10  min. 
at  full  heat  of  a  Bunsen  burner.  This  treatment  was  repeated  to 
constant  weight. 

The  residue  in  the  distilling  flask  was  transferred  to  an  Erlen- 
meyer  flask.  A  white  crystalline  solid  was  noted.  It  was  probably 
lead  chloride  as  it  was  completely  soluble  in  hot  water.  The  volume 
was  made  up  to  200  cc.,  ammonium  hydroxide  being  added  to  give 
a  concentration  of  1 :3.  Hydrogen  sulphide  was  passed  until  the 
solution  was  saturated. 

The  black  precipitate  was  filtered  out.  The  yellow  solution  was 
acidified  with  sulphuric  acid  (1:1).  One-sixth  volume  of  sulphuric 
acid  was  added  and  the  solution  was  saturated  with  hydrogen 
sulphide  after  being  cooled  to  room  temperature.  The  flask  was 
stoppered  and  allowed  to  stand  over  night. 

The  precipitate  was  treated  like  those  described  above.  The 
residue  was  labelled  "Residue  NH4HS  Extraction".  The  filtrate 
from  this  precipitate  was  saturated  with  hydrogen  sulphide  and 
allowed  to  stand  several  days.  The  precipitate  was  filtered  and 
treated  to  form  germanium  dioxide.  It  was  labelled  "Residue  from 
Filtrate". 


46 


£*- 


a     0»C:3^Z     £      « 


Jo 
o 


+       +       + 


RU 

a 


Is 

O 


"d 


o 


0  0  0  0 


S    S    S    §    a    8 

000000 


i-11 
;  g 


•a^ 


§       8 


i  i  i  i  I  i 


iO  *C 


co  ^ 


47 


The  residues  after  evaporation  with  hydrochloric  and  sulphuric 
acids  were  tested  by  means  of  the  spectroscope.  The  remaining 
residue  was  tested  by  the  Gatehouse  test  for  arsenic. 

In  Nos.  4  and  5  the  first  and  second  distillates  were  caught  in 
the  same  receiving  flasks.  To  this  was  added  the  contents  of  the 
safety  flask. 

The  corrections  for  solubility  of  germanium  disulphide  were 
made  as  usual  on  Nos.  1-5  but  gave  residues  of  the  same  weight  as 
the  ash  of  the  filter  papers. 

Since  no  germanium  was  found  in  any  of  the  second  or  third 
distillates  or  in  the  safety  flasks,  only  the  first  distillation  was 
made  in  Nos.  6-11. 

In  Nos.  1-8  the  hydrogen  sulphide  generator  worked  intermit- 
tently and  the  results  of  the  first  precipitation  were  low.  The 
corrections  gave  correspondingly  high  results  but  the  necessary 
double  precipitation  may  account  for  the  slightly  lower  results. 

In  No.  10  volatilization  occurred  after  the  first  ignition,  due  to 
a  slight  amount  of  carbon  in  the  residue.  The  first  residue  showed 
a  little  dark  color  and  should  have  been  evaporated  again  with 
nitric  acid.  The  figures  in  brackets  were  obtained  from  the  first 
weighing  and  are  probably  nearer  correct.  That  would  make  the 
result  like  Nos.  9  and  11. 

CONCLUSIONS.  The  results  show  that  germanium  is  completely 
distilled  over  by  the  one  distillation  with  hydrochloric  acid  in  a 
current  of  chlorine,  after  having  been  oxidized  by  passing  chlorine 
through  the  potassium  hydroxide  solution.  At  the  same  time 
arsenic  is  completely  retained. 

Passing  the  distillate  through  a  spiral  condenser  and  then  into 
water  which  is  kept  near  the  temperature  where  chlorine  hydrate 
forms,  retains  the  germanium  chloride  perfectly. 

The  germanium  dioxide  formed  appears  to  contain  some  impu- 
rities. Whether  or  not  this  would  be  true  with  materials,  which 
it  is  hoped  may  soon  be  obtained,  is  an  open  question.  Much  of  the 
trouble  appears  to  be  due  to  impurities  which  have  no  necessary 
relationship  to  the  method  described. 

Like  silicon  dioxide,  germanium  dioxide  can  be  corrected  for 
impurities  by  volatilization  with  a  halogen  acid. 


48 


SUMMARY. 


Extraction  of  the  "Germanium  Concentrates"  with  water  and 
ammonium  sulphate  solutions  does  not  dissolve  the  germanium 
appreciably,  thus  indicating  the  probability  that  no  free  germanium 
dioxide  is  present  but  that  the  element  exists  as  an  insoluble  com- 
pound with  some  of  the  accompanying  elements.  Its  apparent  in- 
solubility suggests  the  value  of  further  investigations. 

The  germanium  was  successfully  extracted  by  dissolving  in 
dilute  sulphuric  acid  solution  and  was  obtained  as  a  pure  compound 
by  precipitating  it  from  this  solution  with  hydrogen  sulphide,  con- 
verting the  sulphides  to  oxides  with  nitric  acid,  preparing  potas- 
sium fluogermanate  directly  from  these  oxides  by  means  of  hydro- 
fluoric acid  and  potassium  fluoride,  extracting  the  double  fluoride 
with  hot  water,  and  twice  recrystallizing.  The  separation  was 
proven  complete  by  a  spectroscopic  test  and  Marsh's  test  for 
arsenic ;  by  evaporation  with  sulphuric  acid  thus  converting  to 
potassium  sulphate  and  germanium  dioxide,  combined  with  the 
determination  of  water ;  and  by  the  agreement  between  the  deter- 
mination of  water  and  that  of  germanium. 

Winkler's  method  of  purification  of  germanium  disulphide  by 
fractional  precipitation  always  gave  an  impure  product  containing 
zinc,  arsenic,  and  usually  cadmium.  Germanium  and  arsenic  are 
not  separated  by  ignition  even  when  an  acid  less  volatile  than  the 
oxides  of  arsenic  is  used.  The  determination  of  germanium  in  the 
presence  of  arsenic  by  Winkler's  method  of  fractional  precipita- 
tion, which  has  been  the  method  employed,  appears,  therefore,  to 
be  only  an  approximation  made  more  accurate  by  the  compensation 
of  errors.  The  fact  that  ignition  of  pure  germanic  and  arsenic 
oxides  leaves  much  arsenic  in  the  residue  points  to  the  formation 
of  an  arsenate  of  germanium. 

Zinc  and  germanium  are  not  separated  by  precipitating  the  latter 
with  hydrogen  sulphide  from  a  solution  made  strongly  acid  (6  N) 
with  sulphuric  acid.  The  amount  of  zinc  carried  down  is,  apparently, 
too  large  to  be  accounted  for  by  the  phenomenon  of  adsorption  and 
suggests  as  an  explanation  the  formation  of  a  thiogermanate,  per- 
haps somewhat  similar  to  argyrodite,  and  which  probably  is,  at 
least,  difficultly  soluble  in  sulphuric  and  hydrochloric  acids.  Solu- 

49 


tion  of  the  sulphides  in  ammonium  sulphide  effects  a  nearly  quanti- 
tative separation  of  these  metals,  but  the  conditions  for  such  sepa- 
ration need  further  investigation.  Potassium  and  sodium  sulphides 
do  not  give  as  good  results. 

Magnesia  mixture  precipitates  from  germanium  solutions  a 
white  somewhat  granular  substance  which  contains  magnesium 
and  germanium,  but  no  ammonium.  It  is  nearly  or  quite  insoluble 
in  hot  and  cold  water  but  easily  soluble  in  dilute  sulphuric  acid. 
The  formula  was  not  determined  but  it  appears  to  be  a  magnesium 
germanate. 

Ammonium  molybdate  precipitates  from  dilute  nitric  acid  solu- 
tions of  germanium  a  yellow  substance  almost  identical  in  appear- 
ance with  ammonium  arsenomolybdate.  Its  composition  was  not 
determined. 

Zinc  and  sulphuric  acid  in  the  Marsh's  test  causes  the  evolution 
of  germanium  hydride  as  here  no  possibility  of  the  formation  of 
germanium  chloride  is  present.  The  amount  formed  is,  relatively, 
very  small  as  most  of  the  germanium,  like  tin,  is  precipitated  in 
the  generator.  The  element  forms  a  brown  film  on  the  sides  of 
the  generator  which  is  very  characteristic.  Germanium  does  not 
interfere  with  the  test  for  arsenic,  made  by  passing  the  gas  from 
the  Marsh's  generator  through  silver  nitrate  solution.  The  ar- 
senious  sulphide  obtained  in  the  test  contains  no  germanium. 

Potassium  fluogermanate,  prepared  as  described,  retains  water 
even  after  drying  several  days  at  105 °C.  This  w^ater  is  given  off 
at  a  temperature  of  about  500°C,  causing  decrepitation. 

Potassium  fluogermanate  decomposes  at  about  550°C.  in  a  cur- 
rent of  dry  air  and  at  a  little  higher  temperature  when  ignited  in  a 
closed  crucible.  It  gives  a  sublimate  which  contains  no  potassium 
and  which  strongly  attacks  glass,  thus  indicating  germanium 
tetrafluoride. 

On  evaporating  potassium  fluogermanate  with  dilute  sulphuric 
acid  no  germanium  tetrafluoride  is  volatilized.  It  would  appear 
that  the  losses  reported  by  Winkler  were  mechanical.  Even  the 
evaporation  of  16  g.  of  the  salt  with  dilute  sulphuric  acid  gave  no 
appreciable  loss  and  afforded  a  direct  method  of  decomposing  the 
fluogermanate  for  the  preparation  of  pure  germanium  dioxide.  It 
also  gives  a  direct  method  of  determining  germanium  in  the  salt. 

Methods  are  described  for :  the  determination  of  water  in  potas- 
sium fluogermanate;  the  determination  of  germanium  in  potassium 
fluogermanate;  the  testing  of  the  purity  of  this  salt  by  evaporation 

50 


with  sulphuric  acid  and  weighing  as  potassium  sulphate  plus  ger- 
manium dioxide;  the  determination  of  germanium  in  pure  solu- 
tions ;  and  the  determination  of  germanium  in  the  concentrates  by 
distillation  as  germanium  tetrachloride. 


547<H  1 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


